There's an interesting nuance in D&D next - they've included coup de grace rules (which really only apply to PC's since most monsters die at zero HP), probably out of legacy design habit/simulationist habit.
The thing is, it intersects with clerics being able to heal team members for one HP as a swift action, basically for free.
This further intersects with monsters probably not wanting PC's to keep getting back up on one HP and hitting them.
IF monsters actually use coup de grace on downed PC's, it makes a huge difference to how combat pans out. Win Vs TPK, different. Just try running the one combat with monsters doing coup de grace and monsters never doing CDG.
And WOTC seem utterly clueless of this discrepancy.
I presume WOTC want to make a combat system which, whilst emulating genre a certain amount, is also fun in a wargame/boardgame like way.
If they keep playtesting their boardgame design as if coup de grace isn't there, it's a major design fail. It's massively incoherant. Imagine tucking a rule away in chess that, just because it makes sense, rooks can also move on diagnals. But then running all your playtests based on rooks moving in straight lines? Your playtests would be failing to actual test the game you've written!
It reads as a major suck - I can imagine it - go to a game, knowing the monsters could have picked off a PC here or there, maybe killed the whole party because of it. But nah, were supposed to ignore the coup de grace rule and also tell ourselves it was a battle played to the fullest of the rules and the enemy didn't fight with one hand tied behind their back.
Why bother rolling dice when you just ignore significant enemy powers, eh?