Are there any major objections / reasons I shouldn't just do 100% each time? I'm not sure anyone usually notices the randomization much: it isn't the sort of randomization that can easily cause sudden swings in combat the way, say, a status effect landing or non-landing can. It's true that damage randomization *is* a big part of other roguelikes (DCSS for example has much more randomized damage), but it has never been a part of Demon, nor do I really want it to be.
But, what it does do is make me have to soft-pedal damage a bit planning on unrealistic worst cases that, while quite rare, would result in a player being able to be killed by a high-offense same level encounter in one turn from full health. Since that must be avoided at all costs, I have to make sure it can't happen even if the RNG decides to give every enemy attack the 120% result.
That said, if there are any arguments in favor of keeping it 80-120%, I'm happy to listen.
)
Of course, now it's going to be a special sort of dread when you see an enemy use one...without randomization, the AI will be somewhat better about figuring out when it will work.