Three things:
1) If your hero dies when he is casting thrash, he will teleport back to the unit he was attacking after he revives and finish the attack.
2) Your pathing isnt solid. Part of a wall of trees looks like you shouldn't be able to walk through it, but you can.
3) Not really a bug, but the thrash ability does almost no damage to the golems because it ignores bonus damage.
I lied, I actually have a fourth.
4) There are more tomes of power on the map than the troll can use because he is already maxed out before he gets to the last one.