I have Leia, Ackbar(L), Han, at 7* and Lando at 6* but only Leia and Han are geared up. Working on Lando in the Cantina and will use Lumi for the healer.
My current arena team generally never goes lower than 15 overnight and I've hit #1 a few times although my toons are only 68 right now so I get knocked out pretty quick. Sid(L), Leia, Han/RG, GS, Lumi.
Once Lando hits 7 and they are all geared I'll be switching to the rebels to see what they can do in the arena.