That's… actually a pretty solid roster for a Star Wars All-Star game. I especially like the fact that the characters come from various sources (Legends, Rebels, Clone Wars, video games and the 3 film eras).

If I had to be technical, there might be too much Jedi (which is ironically what Smash players are complaining about right now) there are 21 lightsabers against 11 shooters (+ 3 special/joke characters). The viral TR-8R could be a melee fighter more focused on defense, Jek-14 from the Lego shorts would be more focused on Force moves, Zeb would be a pretty average fighter mixing direct fight and range shooting like Chewie, Hondo could use tricks and bombs to distract his opponent, I bet I can find some moves based on spraypaint for Sabine to distinct her from the other Mandalorians, and then there are Greedo, Jabba, BB-8, Sebulba, …

OMG my Star Wars nerd culture and my game designer ambitions got a bit carried away…

Well let's see what characters work and what don't:

+ Chewbacca: use an unique laser crossbow, brute force melee attack, potentially has some hidden tricks in his bullet belt.
+ Yoda: short, quick combo character, spin jump and great levitation
+ Grievous: brutal, four 360° spinning lightasabers, powerful grab
+ Maul: double-bladed lightsaber, enough said =)
+ Ashoka and Ventress: dual lightsabers, respectively Light and Dark Force powers, the other key difference being that Ventress has a more "symmetrical" style
+ Ezra: lightsaber/gun combo, can potentially summon wildlife
+ Boba Fett: large arsenal, jetpack
+ R2, Jar Jar and Indiana Jones are obviously unique
+ Rex: as suggested by Strange Festive Snickerway he can summon troops and also has a large arsenal and CQC skills
+ Cad Bane: a dark counterpart to Rex, summoning bounty hunters and CQC, but both are totally different