Is this a decent mid-game squad?

I'd say stick with rebels, gets you farther in the long run. Try for Ackbar (until you get Wiggs) Lead, ezra, old ben, leia, and maybe lando. Fulcrum Ahsoka is great but you'll want to star her up when she becomes farmable.

Would also recommend working on empire so you can get r2, and farmboy luke/stHan so you can be ready for commander luke event whenever it comes back.