I have this exact same issue. One invincible Level 16 "Elite Orc Fighter" who hangs around in the door to the wizards house. He was originally surrounded by a bunch of mountain warriors and one immaculate who wouldn't attack him. When I attack him it does no damage.
I can't progress the quest.
I read somewhere else online (steam forums?) that before the fight try to give him a single gold piece and supposedly that clears his status?
