None of them are viable from an arena standpoint with the current meta.
Bariss will help most with GW. Ben can also help in GW (unlike Bariss, you don't need to star him up after unlocking). Chirpa looks fun, but not unless you have an Ewok team going. Lando needs Nute lead and maybe Leia. Kylo is an okay all-around character, decent for getting through DS because of high health.
Because barriss leader ability and rg taunt can protect them till they attack. And then they just kill off characters till round two and by that time barriss has healed.
Replies
Bariss will help most with GW. Ben can also help in GW (unlike Bariss, you don't need to star him up after unlocking). Chirpa looks fun, but not unless you have an Ewok team going. Lando needs Nute lead and maybe Leia. Kylo is an okay all-around character, decent for getting through DS because of high health.
Royal guard
Fotp
Rey
Geo soldier