My Rebel team strolled through to Round 8 on Military Might I. It then took me four attempts to beat Round 8 but I finally did so, unlocking Tier II in the process. I still get to Round 8 with rel...
I did it with Wedge, Biggs, K2SO, Ackbar and Farmboy Luke (all level 82, gear 9-10). Speed mods only on Wedge and Biggs. If you needed four attempts to unlock tier I maybe for now you are not strong enough. Anyway my strategy was to stun Palpatine with Luke meanwhile with Biggs I cleaned all the royal guards.