I dont know if its because im playing online, but when i use trap rat with quill storm / werewolf with harbringer it litteraly hits 1/10 times, even going back to lower level zones is difficult, and in act 2 normal i cant kill anything at all, i can see the quill storm impacts over 50 times on a trash mob and it does almost no damage at all.
I dont experience this while playing a sorc / paladin / amazon.