Phoenix Squad Mirror Matches - Any Tips?!

If you're insisting on playing Pheonix (they're an interesting squad to be sure, but I can't see them working against the top arena teams right now - JTR, EP, even CLS), than the best tip I can give you is to run full offense - both Ezra & Sabine. That should allow for enough damage output to clear out the enemy team, while intelligent decision making will make up for the lower survivability without Kanan/Zeb/Chopper (play around and find out which works best). However, for defense, always change to the defensive lineup - enemy Pheonix teams tie against yours, too.