The way trolls die has always been very clumsy in BG2.
- Because the script making them go down is so bad, you usually have to stop attacking them when you *think* you've done enough damage.
- Even when you've done enough damage, they can regenerate a hit point (I think this is what's happening) and survive. I've had trolls stay standing after a ctrl+y.
- They often sneak in some attacks before falling over, even if you ctrl+y a troll it can get a hit in before it falls.
For this reason, I don't find fighting trolls fun at all and as you may have guessed, I ctrl+y a lot of them as a result. I doubt anything will ever be changed, but I personally think it would be better if trolls died normally like everything else, but perhaps make them resistance to everything but acid and fire.