Strategy for 7* Thrawn tier?

They're at the minimum gear-wise, but a bit more on Ezra wouldn't hurt. I did the event with almost the same but I think G9 or G10 Ezra.

Mod-wise:
Kanan - modded well. No issues.

The other four; primary goal should be +speed stat arrows on all 4, +% protection circles on all 4. For character specific:

Ezra - mod with either 4 Crit Damage or 4 offense mods, then 2 Crit chance mods. Choose based on best possible secondary speed and most + flat offense (# not %). + Offense cross, + CD primary stat triangle. Target is minimum +50 speed.

Chopper - 4x speed and 2x defense or health. Again choose based on secondary speed stats. Chopper needs to be fast (+60-80 or more speed). You'll want +protection circle, cross, and triangle ideally, but at least 2 of the 3 for sure.

Hera - 4x speed, 2x potency. Maximize secondary speed and secondary potency where possible. You'll want + protection circle and triangle, and the key is a +potency cross.

Zeb - 4x offense, 2x potency. Maximize speed and potency on secondaries. You want Zeb's potency to be above 60% AT LEAST.

The real key to the whole event is Zeb. He needs a pile of potency to land daze and stagger. Then, the key is to call him to assist with Hera and Ezra all the time. If the target is already dazed or staggered, Zeb will stun them the second time. If Hera lands expose from her basic, Zeb will also convert that into stun. He's your crowd control tool for the event.

You're going to daze/stun lock Thrawn, and kill the Death Troopers, then healing troopers, then either Thrawn or Stormtrooper, depending on who's closest to death.

Use Chopper and Ezra to clear taunts, and Backup Plan on whoever is taunting. They can eat the fracture and revive.

All g8 is rough on last tier. I had a similar squad and it took a LOT of tries. Check the threads in the event area for kill order.