Arena Team Composition

You should be able to still run your Phoenix in the arena a little while longer, but you're smart to be thinking about your next team.

Wiggs teams can handle the sith teams in the arena at least on offense, but I think you might get the best bang for your buck by working on a Sith/Empire team of your own to replace Phoenix with. Mainly because of the ships that Vader/Boba/TFP/Tarkin run and the fact that you don't have a DS team at all for the DS nodes.

Keep working on Boba Fett. He's just a great toon overall and works great with a Tarkin/Vader Empire team given all the debuffs that get thrown around by those 2. He's also an excellent placeholder for when you ultimately get Palpatine.

You have Thrawn already. EP will be here next month (I'm assuming) and your Phoenix should be able to get him at 7* no problem. Vader, Tarkin, and Boba will round out the 5, and TFP is a good empire toon to be working on anyway. You can use him while you're waiting for the Palpatine event to come around again.

The other benefits there is that they're all farmable from different locations, and they'll give you everything you need for R2D2 when he comes back.

No taunting tank? How it will work on defense?

For now I decided to:
Gear 9 phoenix. Farm 7* TFP and Boba. Store arena currency until i will sure what to farm.