Yeah, I'd say keep going with them until they're all 7* and at least gear 8 (or higher depending on what you want to do with them).
I would certainly make Lando the next guy on the list for cantina once you've finished both Hera and Ezra, and Boba Fett from the cantina store after you've finished Chopper. Boba and Lando are the guys who are going to carry you through your credit heists. The other scoundrels are mostly just filler. STHan can be a good dual purpose toon, so he might be the guy you farm out of the Squad Arena Store after Kanan has reached 7*, but there are a couple decent options once you get to that point.