i am also curious to the answer to this question, at least in theory, who would be a counter?
so far i've got, toons that don't counter or assist (ackbar led rebel, gk, phoenix, etc), or buff others(or group cleanses, so gk/rex/chaze , KRU FO), or rely too heavily on crits (wiggs), or rely too much on debuffing (EP leads)....
the answer is obvious, Boba led bounty hunters to the rescue!
in all seriousness, maybe NS, and RJT (even despite the nerf on buffs and assists, if IllumDestiny pops out, maybe still outspeed and damage Sith team? i'm guessing this is the first thing that'll be tried)
best guess, Vader led, wampa, IPD, thrawn, DN/Boba. maybe switch out thrawn for Sass for speed