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...
IF you're working with a newer line up you could try running Farmboy Luke Lead and see if the Tenacity helps, or go old school with an Old Ben Lead and hope for dodges.