I was trying to make Wampa work for the arena, and found that he pretty much fit very naturally under Rex. Wampa needs to go frequently, and Rex's turn meter boost plus cleanse (+20% on basic for a clean Wampa) means he gets to his roar fast. Plus, his counter chance is amazing, so I just mod Wampa for tenaciy on the cross, to prevent stuns and make him a wall that hits back.
He is also zetad, and the next best thing after Zader that prevents DOTs from being cleansed is Plague, which is why I decided to plug in Talzin. MT is a good counter to JTR and other TM gain teams like Rex and NS. Plague counts as a debuff, so that's another 20% on basic for Wampa.
For Tanks I went with Shore and a zetad Old Ben, to help with the healing against NS teams. Shore pre taunt is crucial against JTR teams, to prevent your Rex from getting ability blocked or stunned. And Old Ben death is like a mini Illuminated Destiny that makes Wampa go mad.
This team holds pretty well on defense against all teams, and I rarely fall below 7-8 overnight in my shard. It really doesn't matter if most of the team dies, as the point is to make sure Wampa survives till the end to let off a roar or two and to polish off whoever is remaining. His AOEs start hitting for 36K by the end of some matches, and basic hits for double that easily with the built up offense.
You have a Clone, Empire, Nightsister, Rebel/Jedi and a Factionless character, so there is absolutely no faction synergy in this team. But it still works great on defense, despite not having the best chars in the game (CLS, JTR, Thrawn, R2, GK).