Just thought I'd add to this thread which helped me immensely as a Jedi Shadow. First, yes, Theron's your best bet here. I tried almost every companion--and had only used Theron once or twice before (so he wasn't even armored up)--but he's the right answer for this one. Instead of running around trying to break line-of-sight, I just stood in one place and let Theron heal me. If I saw the blue circle form under me indicating a big attack, I moved of course, but that's about it. Then don't break any of Stark's attacks--just break his Benevolence heal (it's green) with Mind Snap. When fighting him, I almost exclusively used Project, Telekinetic Throw and Force Breach. It kept me a little distance from him and able to move. Finally, if Theron mezzes him, use Mind Crush to end the mezz while hurting Stark strongly.