The body count in D&D really bums me out, especially when it comes to my players (my kids).
The kill count of an adventurer who makes it to level 20 is only one seen by a small number of machine gun operators in modern times. Soldiers who kill in war have high incidence of PTSD and other mental illness. I have a hard time getting away from that idea that this Robocop II level bodycount really makes the game bleak and sad.
What if
- most enemies stopped attacking after half damage, and tried to reach safety instead
- when you take half your hit points worth of damage you get a level of exhaustion
- when you come back from zero hit points you have a level of exhaustion
- most opponents swoon or cower after 3/4 damage
- if you have killed a person, on a long rest you had to make a flat d20 roll and beat 10+ the number of people you killed or your rest doesn't clear any exhaustion
?
question: does that just ruin D&D or could it still be fun?
Well I think it is fantasy, which has traditionally been about good and evil and good overcoming evil. This is not the first time we have heard this argument though. The violence in the game, along with the magic, was used by the religious activists to rail against and try to ban D&D some 40 years ago.
I get what you are saying, but I don't think it is correct to compare real life to make believe. Make believe "killing" has been around forever with games like cops and robbers and army men and even board games like battleship or axis and allies. While we can debate the moral implications of such, those games don't cause PTSD, nor is there any evidence they lead to any other mental illness or maladjustment. I also think that PTSD itself is more the result of being shot at and being threatened with death yourself than it is about killing other people. I think people launching crusie missiles, flying Drones or dropping bombs kill far more people than machine gunners today and don't suffer the same levels of PTSD.
Considering that combat is a pillar of the game and that many of the class and subclass abilities are centered around combat it will be difficult to remove without changing the fundamentals of the game. Even the name of the "fighter" class is explicitly and specifically associated with violence and the "assassin" subclass is likewise named for something intrinsically tied to the act of murdering someone.
Finally the whole combat system is pretty fantastic. If you stab someone with a dagger in real life that person is likely going to die, and if you stab him 10 times (25 hps damage) he is almost certainly going to die. Meanwhile plenty of D&D bad guys will survive that 25 hps of damage and almost all will survive 1 dagger stab. So if we change the rules to say 0hp means capitulation there is still the problem that we are bashing people with a club 15 times or slashing them with a sword 15 times or literally lighting them on fire or electrocuting them before they "capitulate".
That said, it could still be fun without any death, although some parts would get tough to explain and some people will in fact fight to the death to defend what they have or to take from others and that will get difficult to role play around.
When you get down to it the game is make believe and I see little problem with pretending to kill fantastical evil creatures and beings.