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?
interesting. I reloaded before I started the "war", and indeed one of the orcs did not have any inventory.
I traded him a gold piece. Will report back on the results of that... but it takes 30 mins or so to finish this thing. :P
EDIT:
nope. made sure every single orc had at least 1 gp in their inventory. no effect. whoever said this fixes it is mistaken.
