Quote from Yurei1453 >>

Consider the following two scenarios, from the DM's perspective.

Scenario 1:
"You all are on the road, traveling to the capital city of Queston via ox-drawn cart.  The day is cloudy but not overcast, bright and sunshiny without being overbearing.  There's a beautiful breeze blowing southwesterly, and the road is dry and well-packed given the lack of rain for the last week.  This is a well-traveled road; the going is level and easy.  It looks like it's going to be an idyllic day's journey, only four more before you reach Queston.  Alice."

Alice: "Yes'm?"

"You feel a sudden, horrific tearing in your side, awful in its familiarity.  You look down, and see an arrow in your ribs that wasn't there just a second ago.  You suffer sixteen points of piercing damage, and I need a DC 12 Constitution saving throw against poison.  After that, everyone please roll initiative."

 I actually like this a lot. A matter of fact it's exactly what I did when the players had a "secret" meeting in the City of the Dead with a couple NPCs that were important to them. I didn't attack a PC however, deciding to down an NPC and making the party scramble for cover and dive over the NPC to see if she was going to survive. Not a single complaint issued, even when a couple enemies still Stealth sniped them after initiative rolls.

At our table if you ambush someone, the ambusher doesn't roll initiative. They just win it. Everyone else rolls initiative before the first attack, but no one is going to beat that first attack. 

What really irks me about RAW ambushes is that you are effectively rolling Stealth to surprise someone and then you're rolling Initiative... to surprise someone. You shouldn't need to make the second roll if you made the first because they are resolving the same thing. It makes no sense that the monk would have supernatural wuxia senses after he failed the Perception check that literally represents his supernatural wuxia senses.

So with this rule do assassins ruin our games? No. No they don't. Because ambushes are hard to set up - nigh impossible in scenarios where you're the aggressor into enemy territory (such as a dungeon delving) or against well-prepared enemies who can keep tabs on you. So yeah, I think when you're able to pull off an ambush you should get a fairly generous benefit for it.

Not necessarily, it doesn't. There are tons of examples for example on this page. It's a completely different thing detecting someone with the senses and sensing that something is wrong, and a staple of the genre.

Unless you consider "danger intuition" a sense and thus falling under Perception, which our table does. I mean that's why it's called Spidey Sense. High levels of basically any skill shades into superhuman territory, so I don't see why Perception would be ay different. At any rate, if I had someone sneaking up on Peter Parker and he specifically rolled a check to detect a threat, that check is gonna include his Spidey Sense because that's exactly what Spidey Sense does.

Furthermore, it just feels bad at the table. You're not attacking Spider-man here , sometimes you're just sniping Random Sentry Guy #4. His cinematic turn to catch your arrow feels out-of-scale to the threat he actually represents and comes off more as a DM gotcha moment than a memorable story beat.

It is usually extremely easy to surprise opponents

I guess we just play different games, because at my table it's really not. For us, it pretty much requires an enemy moving into a predetermined area within an expected time window, which requires a lot of knowledge that is nontrivial to obtain and just doesn't come up often in the narrative.

If you're talking about one stealthy guy sneaking in for surprise, after that big hit he's either going to be facing multiple enemies alone or running away to leave the rest of the foes on high alert. The threat of the former situation ending in death and the consequences of the latter is enough to make it a difficult decision.

Now if it was extremely easy to get surprise at my table, I would certainly not be so generous. But it's not, so I am. I can certainly see how our rules might not be appropriate at other tables.

Quote from Yurei1453>>

I do not see how assassins, or ambushes in general, are actually dangerous at all at your table, Lyxen.  The rules that you and those aligned with your views seem to be espousing is that an entity which is about to take damage from a theoretically 'hidden' attacker must be informed exactly what is attacking them via what method and from which position, so they may know exactly the correct way to respond to this "Ambush" attack.  Stealth is meaningless, and 'Surprise' doesn't truly exist save as a mechanical condition extremely unlikely to occur. 

The person who gets surprise always get to act before the person they surprised, and sometimes even twice (depending on initiative)! That's pretty powerful!

@FTL: Similarly, having players roll initiative for a road ambush they were not aware was happening destroys the ambush scene.  Players who roll initiative above their enemies are told "Okay, take your turn, but remember - you have no idea what's happening, where your enemies are, or that anything is wrong." 

Except if they're surprised, they don't do anything on their turn besides losing surprise, so you don't need to tell them to take their turn. This thing you're saying would happen "take your turn, but you don't see anybody"  - never happens (at least, it doesn't happen for this reason). The first thing that happens is always the enemy action - it's just a question of whether the PCs have their reaction available at that time, and whether the enemy gets two actions in a row to start or just one.