Why are you only doing tier 6?
Off of just what you have, you might try Teebo (L), Phasma, TFP, Rex, and a fifth...but you might also try your Zader squad of Zader, Sidious, Boba, Rex...really, you might be ready to solo Heroic rancor. If your guild has a few other tmr squads, you should really convince them to try heroic.
P.S. I'm running Teebo (L), TFP, QG, Phasma, and Jyn. Teebo and Phasma are g8, and TFP is g9 (and growing). I can solo p1 with the boss taking 0-1 turns. Don't know how I'd do whole thing-wise, as it's against how our current raid rules are set up. But I imagine quite a bit, especially as I gear the lower three and remod everyone.
Seriously, try heroic.