At the final stage, where the three ghosts attack in sequence, I beat the first one without too much effort, but the second killed my creature about 30 times before I finally won, and then the third went down like the first. It kept shouting across the room, throwing my idiot all over the place and then filling the body with arrows. After a certain amount of healing potions I realize the better fighter has won and accept the harsh fate of death.
Eventually I used a storm atronarch staff to divert their attacks and identify the master, while I used weak firebolts to support it, since bows seemed too slow, and I felt terribly cheap. And then for THAT I needed about three tries. This after I had locked my follower/pack mule outside the room because I did not want to win too easily.
I remember finding the earlier encounter with ghost/corpse 2 unusually difficult, but I had fewer tricks and items to use, and probably only needed 3-5 attempts. By the time of the second fight my level was 52. Usually being a crummy player has gotten easier with more levels and more items, but perhaps it worked in reverse here.