Hey you will need all of their uniques as high as you can get it. I got thrawn 5* last go around with my alt account and still use him in arena today. I think you can get 5* thrawn but I don't think you will be able to get 6* unless you are lucky.
Ezra, CD and CC, Speed mandatory
Ezra is your only continuous damage so you want him fast and hitting hard. Everybody elses job is staying alive.
Kanan, health and defense, can be slower
His taunt lasts a while and he has a heal so its okay if he is slower. I didn't say slow, as every turn will heal him more, but can be slower.
zeb, health and potency, can be slower, you will call him to assist often.
Two things. Zebs unique makes it so everybody gets a ton of extra protection BASED ON HEALTH, so adding health to any toon because of him is optimal over added protection. Health ends up being a double whammy. Second, he needs potency. Zeb is under utilized. If he has high potency and getting called to assist often, you can land a high amount of stuns.
Hera, health and defense. Speed mandatory
Leader, dies easier, and she is the only one who cant res. You want her fast so choppers turn based heal will keep her up to par.
Chopper, health, protection and defense, speed mandatory.
Keep this sucker alive and he can take some well needed heat off of Kanan and the others with his taunt and evasion. Surprisingly effective. Chopper is arguably your biggest health supplier. If he dies, odds are everybody else will too as they just lost their largest heals.
Good luck