Another guy lost in the galaxy with his first zeta ;-)

GW just goes by your top five toons.

Sion, even at 3* is a major nuisance to opposing teams. So I'd maybe work on him, plus he'll benefit from Palp lead, Kylo won't.

With regards to ships, assuming you're using Biggs like literally everybody else in the game who slightly knows what they're doing. You'll want Vader out on the field from the get go for target lock spam. Bring KRU in to lay down the hurt once Biggs is tanking. Silencer is a little fragile after all.