Poisons: There are lots of different poisons, with varying lethality. And a poison's effect is incredibly variable (dosage, body weight of target, constitution/fortitude of target, mode of exposure, etc.)
How are you going to take into account things like dosage, body weight, and so no?
IMHO you are just trying to obtain an unrealizable result in D&D.
In D&D high level characters can drink bottles of poisons without any negative effect, no matter their body weight, dosage etc.
Also, very few poisons kill immediately unless exposed to massive doses. In the real world, people survive poisonings all the time, sometimes even without medical attention.
Unfortunately in D&D even poisons aren't realistic at all, and are designed for unrealistic people.
In real life there are no Dark reaver powder, Purple worm poison or Dragon bile.
Acid: Again, this is a variable threat. If it's a pool of acid, then see the rules for Lava
Good luck to your PCs in any dungeon.
An Acid attack however (splashing, spray, etc.) is just Hit Point damage (IMO).
I can't see why.
Fire: Fire also is variable. It depends on the time of exposure, the heat of the fire, mitigating objects, clothing, or a shield, etc.
A list of parameters you can't consider in a D&D game.
Fire isn't usually immediately lethal (which is why death by burning was such an absolutely horrible punishment). So in this case also, Hit Point damage works just fine for me.
But what about a PC trapped inside a closed room in fire?
As to a Giant's club (as I think somebody mentioned earlier), I think the damage potential should be much higher than typically represented.
How many Giant's club hits should a high level character be able to sustain before dying in your "realistic" scenario?
But getting lucky and not suffering maximum Hit Point damage from such an attack is a reasonable outcome. There are a ton of variables in any weapon attack. Even a the attack from a Giant's club. So variable damage potential, modeled by Hit Points also works.
So your PCs are going to face deadly enemies 24/7 because they know they are incredibly
lucky?
Isn't the same thing as jumping from 200' and knowing the impact will not kill you?
But Lava (falling onto lava, as one cannot fall into lava) is almost certainly instant death.
This sounds apodictic.
There are
hundreds of lethal menaces in D&D.
Heck, even a large boulder falling onto an unaware human should squash him like a bug.
Not to mention that, IMHO, a Masonry wall (1 ft. thick) should "survive" to many "attacks".
But in D&D such a wall has hardness 8 and 90 hps.
A high level barbarian has many more hps than a masonry wall.
And Falling Damage, based on real world consequences, falls of 50 feet are about 50% fatal, with the chances of survival quickly diminishing to practically zero very quickly.
I don't want to imagine the
real world consequences of being hit by a giant's club, anywhere on my body.
PCs who must face
real world consequences would never face
real world insurmountable menaces.
In real life no group of 4 people would ever face a colossal dragon, or anything of CR >4.
