While Quinn's betrayal was understandable -- it was rather obvious Baras planted him into your entourage and he never hid his loyalties anyway -- your character's reaction was beyond idiotic. A typical "RRRRAAAAAGE RRRRAAAAGE KILL MAIM KILL RARRRRR!!!!" Sith would have offed him on the spot out of rage. A Sith with brains would off him out of simple self-preservation, because nothing proves the man's loyalties have changed - if anyone bought his "Oh, you choked me a little instead of choking to death as Baras would, so now I'm totally honestly switching sides honest!" spiel, please call me, I have a nice collection of bridges you might wanna buy. A Sith who's all about calculated efficiency would exterminate him for presuming two puny future scrap heaps was enough to snuff Emperor's Wrath.
Now, while he is unkillable due to MMO restrains, thing is it's not even needed - just turn him into empty shell, or a cyborg, or reprogram his personality. There, just one little scene to write and you have your healer and
your revenge too. You don't even need to fix his ambient dialogue, since he behaves like an android most of the time anyway.
(I also wished that if you took him for the final confrontation, he'd side with Baras against you again, both laughing at what a gullible idiot you are.