DeconstructionG 15

I was around lvl 32 with the Ranger when i did this,save up a lvl 3 power attack or take a yellow potion or 2 to fill it up.Soon as the boss spawns take a rage potion(blue) then unleash your power attack.This will kill the boss in 1 hit.Don't stress as the boss is pretty much at the start of the lvl so if you're unlucky enough to get hit it's not much to retry.