I recently had the first big fight of my campaign with my players. I'd thrown some calculator-suggested encounters and the bulldozed them. I had a mass combat with 50 zombies in a church where the zombies were one-hit-killed to make my players feel like badasses. And they were each fun in their own way. But I was ready to have a fight where someone could die.

And it lasted for the whole session. Over 2 hours of combat. Part of that is that my players are less rehearsed with the rules than I'd like, and part of that was I buffed some monsters so they'd last longer. My squishy wizard player pretty much got as far away as possible and lobbed spells at the baddies until he was down to cantrips only, but they made their way over and took him out. He was only out for around 4 or 5 turns. The party won in the end though and there was much rejoicing.

Then I looked up the rules of what the players did (Moonbeam and wildshape, specifically) and realized we were all so very wrong about it. I told her about what should have happened, and it did not go well. Without our incorrect assumptions of her abilities, she would have been out of the fight way sooner. And then she'd be sitting there the rest of the 2 hour fight watching everyone else play. 

What her complaint boils down to is this: Either she is out of the fight early on and wastes 2 hours of her life, or she's a useless party member because the other 2 high AC paladin and cleric would have just carried the fight. My question for you all is: what do you do about a player who is out of the fight for long periods of time? How do you make spellcasters who are out of spells be engaged in combat? This is a really big moment for us, I think, because she said something to the effect of why is she even there if she's useless to the party.

It's really up to players to make themselves useful when out of spells. They can multi class into more combat heavy classes (Draconic sorcerer would afford her a bonus to AC). However, if she survives, she can still stabilize the players, use the Help action, or otherwise strategically assist the party.

There are also cantrips when out of slots.

I don't think I got my main problem across very well. What do you do if a player is knocked out of a fight nowhere near the end of the fight? How do you keep the player invested and interested when no one can heal them to even let them do anything in the fight? 

On one of the few times I have run across this problem I let that player be the monsters. Now to be fair the player is a exceptional good player and didn't let his bias save the pcs. If anything he went for the throat more then I would. 

Now you have new players, so this may not work for you. A second idea is you could prepare a npc that might get involved. If you know a fight might get nasty have a stand by. 

I would also suggest talking to your player and deciding if they want to reroll a new character. Not every class is for everyone. Not a lot of details in your post but for your specific case maybe rerolling or finding out how she could be get more bang for her druid buck would help.

IMHO, you're trying to manage the Player experience too closely, and you're structuring (a) combat in a fashion which steps outside what the 5e game designer expect, and that they built the spellcaster classes to be able to handle.

I wouldn't try and meta-manage aspects like "this combat is to make the Players feel like bad-asses", or " I was ready to have a fight where someone could die". IMO, that's the domain of the Players, not you. You set up the situations - realistically & plausibly, according to the dictates of the unfolding Narrative - and they knock 'em down. You design the problems; they provide the solutions. You don't have to ( and I'm of the opinion you should not ) build solutions into your problems, either. Part of the Player fun is coming up with solutions to the problems you create. Let your Players play that aspect. It's your setup, it's their story. If you already have a solid idea how the combat should unfold or feel, then you're tempted to try and warp the situation to try and reach that outcome - and that takes control of their story away from the Players.

Don't worry - if they pull off their hair-brained scheme / reckless attack heroically,  they get to feel like bad-asses; naturally, and well earned, not thrown to them as a pre-planned DM gift. If they screw up, then someone can be in serious danger - and that can happen purely at the whim of the dice gods; the DM doesn't need to stack the deck against them to make them feel panicked.

And also, D&D seems to be built around a 3-6 round combat encounter. Artificially buffing the monsters to make the combat a slug-fest - apart from tending to make dull and grindy combats ( unless the DM is working their tail off to make the combat situation dynamic ) -  it breaks the design assumptions built into a lot of aspects of the game, and that's what you're running into. Your spellcaster is running out of resources, because the spellcaster classes were never built with the idea of someone slogging it out in a 12-15 round combat.

That's the problem here: It's not that your Player has a bad Character build, or that your Player needs to work on her imagination in order to stay relevant, it's that you're putting her in situations in which her class design was never meant to be effective.

I'd recommend letting go of some of the control you're holding onto as to how you want, or expect, encounters to unfold, and throw encounters at them which are more "by the book". The Players will find their own terror, and heroism, in their own choices, as they discover their story, in your setting.

Best of luck! :)

Vedexent: I think you might be right in that something with this encounter went awry, but I want to address the broader points you're making here, which seem wide of the mark to me.

I disagree that combats must be short. I think the designers knew exactly what they were doing with the design of each class. Martial classes often have few options, but their attacks are reliable and effective. Spellcasters have more options, and some very devastating attacks, but their spells are comparatively limited. In general, I see nothing wrong with extended or repeated combat resulting in a spellcaster expending their limited resources; in fact, it's an expectation built into the rules of the game. And this division can give martial characters an opportunity to shine.

By design, there are 6-8 encounters in an adventuring day, and by the end of that day, you better bet the spellcaster is going to have almost nothing but cantrips left. Is this also needlessly punishing to spellcasters? Because I don't see how it's appreciably different from one extended combat.

I also disagree with your broader points about encounter design. There's nothing wrong with setting up your players to feel like bad-asses; in fact, most players are going to enjoy this immensely. And reworded, the OP's intention here was essentially just to create a deadly (or above deadly) encounter (one in which a PC "could die"). The OP did exactly what you're asking for in this case: he created an encounter within certain parameters, and then let the PCs knock it down. The only thing he did here that comes anywhere close to changing the outcome was to decide to make the monsters a bit tougher. Maybe it was unnecessary, or maybe it added to the players' experience; I really can't tell in this case.

I also strongly disagree that the DM shouldn't try to create encounters that have a certain feel or that unfold in a certain way. The general "feel" of an encounter is just a part of encounter design. And there's nothing wrong with the enemies having certain tactics that make an encounter likely to unfold in a particular fashion. As an example, one might design a "boss" encounter that's harder than normal and that's likely to be fought in stages. Would you consider this to be inappropriate? Similarly, if you're creating a problem as a DM, you'd better hope you have at least a few potential solutions in mind, or what are you going to do if your players get stuck?

The general point you're making here, that DMs should let their players completely up-end planned scenarios and devise their own solutions to problems, is a good one. With this, I heartily agree. But your argument also seems to be driving at an idea that any planning or encounter design on the DM's part is railroading, and I want to be clear how wrong I think that argument is.

Also, this idea that a character was put into a "[situation] in which her class design was never meant to be effective." What does this even mean? D&D involves all kinds of situations where some classes will be more effective than others. If I create a challenge that involves interpreting magical runes, am I punishing the party's Fighter because he doesn't have proficiency in Arcana? I don't think so.

Moreover, there are some D&D players who want the absolute freedom of making their own choices, but there are others who would prefer a clearer story and narrative structure. As a DM, we're asked to accommodate both of these disparate perspectives. Though spontaneity and improvisation are an entirely valid way to play the game, there's nothing wrong with designing specific scenarios, as long as the DM doesn't decide the outcomes or dictate player choices.

I can certainly be wrong :)

Overall, we might diverge in terms of style and preference - so there's not one right answer - but I'll give you my spin on it, which is not meant to imply that what works for your table is wrong.

Consider that - empirically, and historically - the spell-caster did run out of resources, and would have been relatively useless as a Spell-caster ( an experienced and creative Player can still find ways to be relevant as a Character ) - if the rules regarding certain spells had been enforced, according to the OP. And - according to the OP - the DM artificially buffed the monsters to "crank up the difficulty", outside of the RAW; the creatures ( whatever they were ), were simply never meant to be that hard to kill.

The DM changed the design parameters; a problem with available resources occurred. That's correlation, which absolutely does not guarantee causality - but it's suggestive, and a place to start looking. If this happened at my table, I'd do exactly what I suggested: run a few combats design "by the book", and see how the spell-caster fairs in terms of relevance. Maybe that wouldn't change the Characters effectiveness, after all - although I'd be willing to bet heavily that it did.

My comments had nothing to do with the designers not knowing what they were doing. They may have, but this example is outside RAW, by admission of the OP. This what is meant by a "[situation] in which her class design was never meant to be effective". Class is designed to be effective with these rules. Rules were changed. Class stopped being effective. Again, only correlation, but still very suggestive. 

As for the extended "adventure day" - I am extremely skeptical about the oft quoted "6 to 8 encounters per adventuring day". I think that's been quite convincingly been shown to have been meant as an upper limit. Regardless, I have never seen any online stream, nor has any game I've DM'd, or played in, maintained anywhere near that number of encounters between long rests. And, with Arcane Recovery, even a short rest can allow a spell-caster to reclaim some of their spell-slots; such is not possible within a combat. Rests between combats make multiple combats markedly different from one huge combat, from a spellcaster's perspective. 

As for setting up a "feel" for a combat - I completely agree that you can - and IMO, should - give you Players the opportunity to be heroic bad-asses. You can give them combats which are likely to be grimly deadly.  That's not how I'm reading the OP, however. The OP seems to have "stacked the deck" to try and guarantee that they get a situation where they feel that way. It's a matter of opinion whether or not you think that's OK - but I think that if you're going to do that don't get caught . 

If I were a Player - and I could tell the DM was handing me easy combats ( one shot, one kill, minions ), I wouldn't feel much in the way of accomplishment for winning. I wouldn't feel like a bad-ass. And if the DM decided to set up a "challenge", not by designing a harder, more complex, and more challenging encounter ( more creatures, more challenging environment, integrated creature tactics ), but just made the creatures harder to kill by stuffing more HP into them - effectively taking away my effectiveness in the combat, by making my combat actions less effective - I'd feel cheated. Like I said - don't get caught - but the best way not to get caught is to not do it.

I personally disagree with the stance "if you're creating a problem as a DM, you'd better hope you have at least a few potential solutions in mind, or what are you going to do if your players get stuck?" My answer: they get stuck. They withdraw, they find another way to approach the problem, and they try again, or try a different approach. I won't hand-hold my Players. It's possible to lose in my games. If you spoon-feed your Players, so that they can't possibly lose - because if they flail around and look helpless enough, the DM will give them a solution - what value do their victories have? 

I don't handhold my Players, I don't spoon-feed them solutions, I don't make my adventures a choose-you-own-path novel. Their victories are earned ones, their solutions are ones that they created, and if they fail on round #1, and come back to win on round #2, that's their accomplishment, not a contingency I built for them. When they win, they've earned the right to feel like bad-asses, because they were.

To quote/paraphrase Matt Colville, "I'm not here to mange the Players' problems; I'm here to manage their solutions".

Conversely, I don't cheat them - I won't suddenly change up the nature of the world ( giving the creatures more HP ) to make things harder on them. If I want to make things more difficult, I'll do it within the parameters of the narrative, and the world that they know: the bad guys got reinforcements, the situation got more complicated by other people getting involved, there is now a deadline for some in-story reason, etc. 

I also disagree ( respectfully ), with the stance "As a DM, we're asked to accommodate both of these disparate perspectives". I don't think that you can - or should - DM effectively outside of the style that suits you, as a DM. I think the hobby of TTRPGs labors under the delusion that under a good ( or masochistic ) enough DM, any RPG group can work. I'm of the opinion that you should find Players with whom you all share a compatible approach to the game. In the era of Roll20, and other virtual tabletop environments, this is completely possible.

Again - this is all my stance, and my approach to my game. If you don't want to follow it, that's completely fine. All that means is that we have different styles and approaches to TTRPGs. You seem to favor a more managed and curated game; I am more for an open-ended simulation style approach. No problem there - we don't expect everyone to like the same kind of cuisine - why should we expect everyone to have the same ( or even compatible  ) approaches to TTPRGs?

All I'm trying to communicate is my approach to the game, here.

This occurred in session 4. In session zero, the players had easy combat to ease them into their characters and give them some sort of common bonding point. Then they tracked down a bad guy, handily defeated the encounter that should've been a medium difficulty. Session 1-2 Went to a church overrun with [DM Weakened] zombies that... I don't think the players took more than 10 damage total. They were very good at tactics on that battle though. The feedback I got from the party was that they liked it. So the situation that unfolded was my players had come across a werewolf village. The werewolves were not aggressive, just hoping to live their lives without being hunted and hated. They picked up an Assassin NPC who Session 3 they had an admittedly poor social encounter with the leader of the village, solved a puzzle that was lackluster, and then got a little railroaded into a fight with a corrupted werewolf who had recruited some other werewolf-supremacists. 

At this point, none of the party had even been at half health. I wanted to challenge the players, making them use their abilities and spells smartly. The encounter in Session 4 was 5 werewolves not altered and 1 leader werewolf altered. I used the BBS Captain/Werewolf from homebrewery.

I don't know if this is relevant, but I'll my Level 4 party layout here. 

 The party did a bless/bane combination. The werewolves could barely hit the paladin. The druid was in the thick of the fight to utilize thunder wave. The wizard got far far away and lobbed spells. The cleric was pretty much ignored by werewolves because the paladin and druid are pulling the werewolves. 

After some more discussion, the druid feels left out because, while she dealt the finishing blow on literally every werewolf, most of her damage was from moonbeam. But we read moonbeam wrong and did damage every time a creature was touched by the beam. As in, she dragged the beam across a few werewolves, did 2d10, then left the beam on a werewolf and it took 2d10 again. THEN as a last ditch effort, she turned into a direwolf using her wildshape. She regained HP because of it and dealt a lot of damage in that form, still almost died. In her words, "Without us cheating, I would have died." I told her that at that point, the paladin and cleric were pretty much good as new. The wizard was stable. The party would have won the encounter if she went down. THEN the issue became "If they carry the party, why am I even there?" She usually has problems paying attention and staying focused on the game. This was the first time she was engaged during combat, and it was bitter in the aftermath because she "shouldn't have been that good." 

I hope this more thoroughly explains my issue. Thanks for sticking with this issue. I really hope I can be a better GM after this. 

A level 4 Circle of the Land Druid can't wildshape into a Dire Wolf, as they can only Wildshape up to CR 1/2, and the Dire Wolf is a CR 1 monster. A non-Moon Druid is mostly a support caster, using spells like Spike Growth, Moonbeam, Fog Cloud, or Web (Underdark Land Druid only). If she wants to be the primary damage dealer or tank for the party during combat, then she picked the wrong type of Druid, or even the wrong class entirely. This mostly comes down to a difference in expectations of the player vs what the class can actually do.