1) Get a full stack of trolls. (Don't use ANY other stacks.)
2) Make sure you have Stone Skin, Avenging Angel, and Mana Spring Level 3.
3) Keep Stone Skin and Avenging Angel on trolls. (Slap on whatever physical resist stuff you have too)
4) Use Mana Spring if running low on mana.
5) Just attack with trolls.
6) ???
7) Profit!
As long as you keep attacking him, he won't summon any droids. I did this with 1 troll on impossible (Avenging Angel and the occasional fire arrow did most of the damage), so you should be fine if you have the spells.