First, a hit on a PC at 0 is two failed death saves. Two hits and you are just dead. Period. No need to do 40+ damage. Two hits of 1 point each is sufficient. Second, if the monk goes down rapidly due to the rolls I describe above, then the rest of those hits and crits can easily drop a second or third PC to 0.
Remember, the party can easily have been beat on for a few rounds before the dice get hot and/or cold for the PCs. You are white rooming what we are talking about and combat is not a white room. It's not possible for you to sit back and come up with a simple neat model like you have been trying to. There are too many variables for you to model it.
You're missing my point. I'm absolutely not saying that PC's can never die. Of course not. But, if you start attacking downed PC's, and every attack (at advantage no less) misses, it's pretty obvious that you're fudging. And, I'd go so far to say that if the DM does start attacking downed PC's, then he's very likely not going to fudge, since he's actively TRYING to kill PC's.
It's got nothing to do with theory crafting or white rooming. It's the simple fact that, outside of a couple of exceptions, no monster of CR 5 or less can do enough damage to the monk to flat out kill him. Nothing can do 41 points of damage (minimum required to go from standing to dead for our 40 HP monk). The Wraith is an exception since it removes the buffer of negative HP. You die at zero. Effectively, a wraith is doing double damage on a failed save, since you are twice as close to death compared to any other creature.
MaxPerson said:
If there are three trolls, you can have crit, hit, miss, hit, crit, miss, hit, crit, hit,
Read more:
http://www.enworld.org/forum/newreply.php?do=newreply&p=6816107#ixzz3zF9rlEkr
The point is, the odds of that actually happening are still about 1 in 8000. (Ok, they're slightly better than that, but, not by very bloody much). This would be a once in a campaign level event. If this sequence occurs more than that, there's something going on. Like I said, probably using a more difficult encounter vs the party to give that "one and done" feel to the campaign. But, the results you're getting are DEAD ON what is predicted by the system. 3 trolls vs a 6th level party of 5 PC's is Deadly. You
should have dead PC's in this encounter. The DMG defines Deadly as:
DMG said:
DEADLY - A deadly encounter could be lethal for one or more player characters. Survival often requires good tactics and quick thinking, and the party risks defeat
This isn't an example of extreme luck making the encounter wonky, this is an example of the rules working
exactly the way they are supposed to. If you feel you have to step in at this point and "adjust" the die rolls, why did you use an encounter that the game is telling you is quite possible to kill PC's? And, again, this is speaking directly to my point. The DM is using encounters above the weight class of the party, the encounter goes sideways, and now the DM feels compelled to step in.
It's almost like the game underwent a couple of years of development by a bunch of smart guys that actually understand math. What a shock.