I had my troll armor upgraded to lvl 3 I think..no cape yet. My finewood bow was lvl 4. I had built a base below the elder platform, and the area was mostly cleared of trees as a result.

Behind most of the large stones, I dug a small pit. I just stand behind the rocks and snipe with fire arrows until he either destroys the rock or summons those lashing roots (then I Must move to another rock). Its a very easy fight, I hardly took any damage. I didn't melee at all.