If you run TFP then you shouldn't need to stack potency on anybody.
Oh, and I run Zader, TFP, Tarkin, Teebo, R2. I like Tarkin for a few reasons: he has a chance to reduce turn meter as an Empire character under Zader lead; he does decent damage and has good survivability and speed; he can reduce 50% turn meter as a backup option whenever Teebo gets resisted; he has a zero-damage special ability for close calls where you don't want Rancor to gain any bonus turn meter; and, perhaps best of all, he inflicts Critical Chance and Offense Down which greatly reduces Rancor's damage when he occasionally lands a hit.
