Actually someone else had trouble with trolls too, so it's not that unusual.
I've found the game goes a lot faster if I can get a bunch of enemies to follow a decoy with free movement into a web/entangle trap and then rain holy hell on them with spells and ranged attacks. The speed boots help a lot with this approach.
But this breaks the game when regular or snow trolls are involved.
Other approaches are so much more tedious.