First and foremost Barbas CANNOT DIE! (Now maybe this is a glitch?) but I am ok with it.
Barbas is quest essential -- not a bug or glitch.
Seriously, it's the Masque of Clavicus Vile versus the pleasure of axe-murdering Barbas--that is no small thing to give up. I've stayed in character twice so far and took the mask, but I think I'll feel more satisfied with the axe.
I didn't even know about the masque when completing the quest, and Barbas pissed me off so bad on the way to finishing it, I couldn't wait to kill him quite honestly. On my "less-chaotic-evil" thief, I'm sure I'll let him and Clavicus get reaquainted.