As for the Skull Cave fiasco, I fell victim to that. I found and explored Skull Cave before getting the quest about the Blackfang chest. Since I didn't have that quest, the chest wasn't triggered, so was not there in the cave. Later, when I did get the quest, the chest still wasn't there. Hence, I couldn't progress any further in the game.

Uh, maybe the Duncan you have to find is the imposter, since the Tomb-Duncan is apparently the real deal. I never finished the Tomb quest. My barb-barb-rune-druid party got to poor old Duncan before he shuffled off this mortal coil, so heard his dying words. It's saved, so maybe I'll go back and check it out.