First off, I dont know if this works anymore since it was a while I did it. Just came to think of it and thought I should post it if it might help someone.
My brother where to do the epic priest quest and I wanted to see what it was about. So I just stood beside him and watched him, when I suddenly got hit by something. My brother then said I had a ghost hitting me, so he came really close to me, and alot of ghosts started to hit me instead of him. I couldnt see them, but I just stood still and used mana shield and HP pots, while he was running around doing the quest in easy mode. I didnt dare to move or do anything, since it might have failed the quest for him, but it made it alot easier to do the quest without having the ghosts hitting him.
Hope it works for you if you are to do the priest quest.