New mage is so buff???

NPC Spellcasters have no Spellslots. Only daily uses. This is interesting for Counterspell, as it can counter the spell, but retains the spell slot of the countered spell. Since NPCs don't have spellslots, they loose their use. So Counterspell is stronger against NPCs than against players. And as we can see here, the mage can use counterspell only once. Paladins should rejoice that mages won't counterspell all their smites now.

As a DM I have had a lot of success using pre-written modules with default NPC stat blocks to run complex, session long encounters that feel earned and give all my players an opportunity to shine. When level or party size adjustments were needed, I found the DMG guidance for CR budget surprisingly accurate. When running "boss enemy" casters I found they make more interesting adversaries if they get to use at least half their spell slots and that it is the concentration spells that really make the encounter feel dynamic and special. I ran at least 4 encounters with NPCs using the old Mage template and in every case encounter terrain and minion changes were enough to add a lot of individually to the encounters.

In the prior iteration of Mage it was defensive spells like Greater Invisibility and Misty Step that really defined the encounter and allowed the damaging spells to start putting pressure on the party (especially given AOE spells need all the help they can get positioning wise). With my group Fly on its own wouldn't allow this iteration to survive the round. I get the daily spell approach limits options making it simpler to run for newer DMs but would have appreciated an optional entry for standard caster blocks with intelligent spell choices.

TLDR - I feel like this version of the Mage gives me fewer tools to run interesting and reactive encounters without investing time into customization.

I wholeheartedly agree.

Analysis paralysis was an issue, and some spells can certainly be cut, but at least give TWO concentration options in combat (not counting suggestion and detect magic which are pretty much a waste of a mage's turn).

Given that Force seems to be the typeless damage that nothing is going to resist (unless Brooch of Shielding works the exact same way), maybe don't have that be the default damage that every spellcasting NPC can deal at will? Alternatively, give two at will spell attacks, one of which is elemental (and thus, might be resisted) and the other is force but also weaker.

Also, don't have the at will attack be melee or ranged. Have it be one or the other. Or, going by my above suggestion, have a separate attack for melee and range so they feel different. Arcane casters generally want to stay away from the front lines. That's battlefield tactics 101.

On the whole, though, I do like this. When I run Curse of Strahd, I'll have Kasimir and Victor use a similar statblock, though I'll modify their spells. For casters who can switch their spells daily, I'll have the NPC versions able to swap out some of their limited spells if it seems reasonable they could do so.

I like this a lot. It was overdue to have spellcaster NPCs that don't just die in one round to appropriately leveled parties. Having AC 20 for two rounds combined with the 81 HP makes the mage much more durable than it ever was.

Why not count suggestion? Suggestion could completely take a player out of the fight. 

People freaked out too much about Counterspell affecting monsters, without taking a moment to realize exactly what you just said. Reactionary responses should often be ignored; critically analyze first, then speak up. 

Yeah, these guys are gonna be fun to use.

People make to much of a deal out of counterspell not giving monster casting uses back. 

A DM is under no obligation to use these statblocks as written. You shouldn't assume it only has a certain number of uses of a spell. The point of that change to counterspell is to give players their slot back while not adding unnecessary extra text to the spell. 

I am curious about the Arcane Burst ability that is shared by this monster and many other arcane encounters. Arcane burst seems to have a unique set of features in that it is useable both at range and as a melee attack. If all of these spellcaster monsters have this ability why isn't Arcane Burst available to player characters?

I will not use nor face any new rules spellcasters until my pc wizard can also use arcane burst and it scales the same way.

The reason Casters don’t (and should never) get an Arcane Burst equivalent action is because spell casters are already strong and versatile enough as is, they don’t need what is effectively a super powerful weapon attack as well. They have cantrips for a reason.

Arcane Burst, and attacks like it in the new MM, exist to simplify a statblock so I (as a DM) don’t have to look up 15 different spells per turn when running a caster enemy. If you look at their Spellcasting list the options they have are some of the most well known in the game, to the point I don’t even have to look up most of them. It’s a huge timesaver when running the game and gives magic user monsters a solid consistent DPR.

Quote from Tactical_sarcasm >>

The reason Casters don’t (and should never) get an Arcane Burst equivalent action is because spell casters are already strong and versatile enough as is, they don’t need what is effectively a super powerful weapon attack as well. They have cantrips for a reason.

Arcane Burst, and attacks like it in the new MM, exist to simplify a statblock so I (as a DM) don’t have to look up 15 different spells per turn when running a caster enemy. If you look at their Spellcasting list the options they have are some of the most well known in the game, to the point I don’t even have to look up most of them. It’s a huge timesaver when running the game and gives magic user monsters a solid consistent DPR.

 Just give them a damn fire bolt or ray of frost and put it in their actions in addition to the spells they can cast. Facing an ennemy spellcaster, specially humanoid, should feel like facing what your PC could be/could become. A lvl 12 wizard facing an archmage should see this as facing of what he could become once reaching higher level/become an archmage themself, not just an other random ennemy with "I cast piew piew prepare to meet God." I like humanoids to have sheet that almost feel like PC, so the players can really compare to them and feel invested in their character, to see where they could locate themself compared to my world.

And really. As a DM, I never had any problems following the abilities and spells of my spellcasters, even less in fact that for many others statblocks cause most spells have effect well known while some creature niche abilities can be way more obscure... Well, the fact that as a player I am a wizard and cleric main also help, since I exactly know how almost every spells works. But, even if there is no spellcasters ennemies in your campaign, i think its required for a dm to be able to easily follow the functioning of spell slots of a creature and how most spells work.

I'd say this makes more sense to use as the new drow mage instead of the bandit deceiver.

I don't know how I feel about this.
There's both good and bad here. 
Most of the bad is theoretical and vibes based though so... I guess it's good? Ish.

Okay so I have a question for everyone, how exactly do you capture one of these guys if they don't want to be captured? Party wanted to capture him alive and bring him back to town, and did the reasonable thing and cast silence to remove spell casting since it was an ambush. Party then got kind of annoyed when they realized that silence was pointless since the mage was able to just spam arcane burst, so the fighter wanted to make a disarming strike to get rid of arcane focus, found out NPCs don't work that way and just knock him unconscious next turn. After the fight ended however, my player asked me out of character how exactly this works, since if the mage doesn't need to speak or have any components at all then he cannot be disarmed or made harmless, putting him in jail doesn't work since he could just blast his way out and Anti-magic is super high level so not exactly common for local jails. He said he didn't want to mess up the campaign, but his character has now seen that he cannot disarm the mage or make him unable to cast just by gagging him, which is normally the go to for captured spell casters in past editions, so as far as his character is concerned that means every enemy spell caster has to just be killed no matter what their crime since you could never safely put them in prison or even capture them to bring back to a prison. If he woke him up to interogate him, what could the party do to make sure he cannot just attack immediately, since as far as I can tell arcane burst doesn't actually need limbs it may just fire energy from the mouth or eyes so the mage could attack as soon as they wake him up. No wall is unbreakable, and being able to spam arcane burst would break any non-magical wall or iron door/gate eventually, and probably pretty quickly if we use wall of stone as a baseline for stone wall stats, so he was right in that regard that the local jail couldn't realistically hold a mage. I honestly didn't have an answer for him so I just house ruled that the mage needed somatic components so if they bound his hands, he couldn't use arcane burst, but what would you all do?