Dooku and Sith Trooper for their counter-attacks and the health steal make them solid choices for a Nihilus lead. Savage Oppress misses out in his HoT but he is still gaining essentially perma-offense/defense up, still dispells an ally every turn and still cleanses himself when he is crit. He brings plenty of utility without the HoTs and the inadvertent side effect of no HoTs is he is less vulnerable to Boba nuking him.
If running that style of team I probably run Darth Nihiuls (L), Savage Oppress, Dooku, Sith Trooper and the fifth is a flex spot. Go with Sith Assassin to ignore protection and setup early Overpowers from Savage. Go with Emperor Palpative for Shock/AOE Stuns and a slightly softer target for enemies. Go with Darth Maul to gain Daze, max health gains and solid damage. Of course that is if you want to go with an all Sith team, if you are mixing/matching then the options are much broader.