What is the best team around GK and Zarris?

Was using Gk lead Zarris r2 dn Thrawn and doing great no losses against the strongest cls comps but top comps in my shard now have there toons all g12 made huge difference was getting wrecked so I put in Rex for r2 and now I'm back to no losses against them. Rex tenacity up stops all the r2 stuns the tm gains help dn annililate faster plus when Rex uses a special he goes stealth works great