Mods.. the true meta?

Yes a rex team can beat a sith team with vader, but if they have speed out the wazoo then vader goes first, then culling blade then if he has DN sped up (which he would as a speed focused team) there go your abilities followed by a fracturing of rex who then can't cleanse your team or if you have GK then no worries. They're no longer taunting due to fracture and rex hasn't popped tenacity up yet because it's the sith team's turn still and there goes good old EP with some stuns (admittedly RNG based) but now it's maybe your team's turn. Those who aren't stunned or fractured who by the way can't use an ability yet due to DN who is coming for you shortly. Vadar doens't get in 4 turns before you, but it's not him you need to worry about. His team gets in 4 turns before you do.

Sure a rex lead can beat a sith team, but guess what they need to do it? Speed. Maybe Zadar get's his cull off, but if you've maxed speed out on a few you still may get a turn in before DN or EP, but not if you don't have speed. Good old smexxy rexy is sitting high in our arena right now, but I'll give you 3 guess as to what is maxed out on all members of that team and your first two guess don't count.