Finally did it. You just have to keep at it. You can do it !!
The thing that seemed to make a difference to me, was taking the speed arrow off kanan, replacing all mods I could with protection primary, and putting a crit avoidance arrow on him. I could instantly tell his survivability went up, and put backup plan and taunt on him whenever I could.Same with Zeb, although I did keep the speed arrow in the end, best protection secondaries and primaries you have.
I used the protection up specials for zeb and kanan to protect anyone low health.
I taunted kanan whenever I knew I could put backup plan on him soon (check hera's tm)
I never used Sabine's AoE, as i'm assuming that gives them all turn meter.
Once DTs are down, EVERY assist from ezra and hera, call in Zeb. Dont think calling Ezra with more damage will help, it wont. You want Zeb's Daze to land twice to stun people (especially Thrawn at the end).
For DTs, if they have high tm, or are already dazed call in Zeb. If low tm, call in Sabine.
If Kanan or Sabine die, its not the end of the world. But You really need Hera, Ezra and Zeb to get Thrawn down. I had just those 3 left and 3 of them, and managed to do it. Thrawn was stunned a couple of times with the assists.
I used Zeb's stagger on the DTs if his protection up was on cooldown.
Kill order as everyone says. Detaunt ST, DTs, Finsih ST, Others, Thrawn.
Not sure these are perfect, but in case this helps anyone, here are the mods.
Ezra G10: 210 speed, one health set, one CD set. Speed arrow, Prot circle, CD triangle
Hera G9: 197 speed, one defense, one health, one potency set. Speed arrow, Prot circle, CD triangle
Zeb G8: 159 speed, one potency, 2 health sets. Speed arrow, Prot circle, Prot triangle, Potency cross
Kanan G8: 95 speed, 1 health, 1 tenacity, 1 CC set. Crit avoidance arrow, prot circle, triangle and cross.
Sabine G8: 172 speed, 1 crit dmg, 1 health set. Speed arrow, crit dmg triangle, prot circle.
Ironically my winning run i'd actually left the cross off Sabine entirely, as it was a protection one, and I put it on kanan. She died pretty early.
Good luck guys, keep at it !