Mods, definitely mods.
I didn't find 6* especially difficult but I'm level 80 now with 5 dot mods across the board and some lovely Omegas.
As I'm sure you've noticed your opposition isn't exactly slow which means you can't afford to be either. So yeah, maybe spend the next few days farming whatever 5 dot mods you can though those are expensive.
TBH though, I recall income not being overly forthcoming at that level (it gets worse btw). I'd settle for 5* for now. I'd not worry about 6* too much. Starring isn't a HUGE deal compared to gear and mods.
Thrawn however he comes isn't exactly terrible and you'll still get some good work out of him once he's tooled up. Game is set up so you won't necessarily be able to get all the things first time through.
