Even classes that are slightly worse at using a lightsaber should be able to destroy him. Maybe if you 100% powergamed force powers with min str + never got the obviously hugely powerful buff powers he'd be hard, but I think you could overpower him with force then (can't remember if he's actually immune, I though he just had good saves?). Plus the force drain thing works on the guys in stasis so if you have that you're golden.
I don't think he's completely immune, he just has ridiculous saves and the Force Immunity power. The upshot is that he's pretty weak against lightsabers, but extremely tough against Force powers. A minmaxed Guardian will whack him easy-peasy, a minmaxed Consular -- especially light-side Consular -- will be in real trouble.
He's not unbeatable of course, I beat him on hardest difficulty with said minmaxed Consular. It's just a huge difficulty spike -- up to that point it's Stasis Field and Destroy Droid on everything, with that fight it's manic self-buff, self-heal, and kite while chipping away (=mostly whiffing) with a lightsaber. If you're packing some of those grenades that glue him in place it's easier, if not it just takes a long time, is really tedious, and you can't afford any mistakes.
IMO they should've tuned his immunities so that said minmaxed Force consular would be able to get through his defences with Force powers. As it is, they just don't work.