Sith Zetas

Nihilus' unique is huge if you're going to put sith assassin in. She does massive damage and ignores protection. I've gotten General Kenobis below 50% health to crush with Savage without having to bother with his protection thanks to this. It can also be pretty exciting to see raid han or cls' health look like that of an opponent from about stage 6 of ds/ls battles, especially when you can ignore protection. I'm sure there's a similar effect if you pair him with nightsisters. I actually remain relevant in arena with sith. I prey on General Zariss teams on offense with Nihilus lead, then switch to Maul lead on defense... not because no one can beat it, but because it's annoying enough to fight that people often leave it alone even in the teens/20s.