If the DeathTroopers are hitting way too hard you aren't making sure to clear their buffs ASAP. If it seems unbeatable, your priorities are probably out of whack:
1. Put survival over attack. Use protection regen abilities rather than getting a killing blow in
2. Wipe Death Troopers's buffs ASAP. They will slaughter you otherwise. They can be removed with buff wipes and stagger.
3. Kill DTs
4. Kill Stormtrooper Commanders
5. Kill Stormtrooper
6. Kill Thrawn
Always backup plan whoever gets fractured. Hope Chopper goes first so he can taunt and eat Thrawn's first fracture. Always call Hera with ezra and ezra with Hera. Zeb's daze is nice, but not really until Thrawn is the only one standing since you'll be ignoring Thrawn until then. Always keep at least one taunt up so you can control the damage intake and fractures. Putting bonus protection on just Kanaan is easier than trying to heal your whole team.