Another thing concerning Trolls is now that, for some reason, I seem to be able to hit them dead. Was this originally intended? If I coordinate the Acid Arrow right, you can easily get more experience. Even in case I don't, there is still a red circle around the fallen Troll. TAB give me: Spirit Troll, Dead. He then dies after about 3 seconds.
Or he gets back to full health and you'll have to fight him again. I'v had those multiple times in the D'Arnise Keep.
Spirits trolls "die" and when you press TAB it says "Dead" then of course i cast a "Acid arow/Fire arow" and that doesnt even hurt him. He doesnt die at all from fire or an acid attack then a few seconds later he's back to full health again. Then you fight him again and he dies normally from Fire or Acid.
It seems that it is only with the Spirit Trolls.