Well, Leia also gets extra attacks from AA's Tactical Genius (and if ever applicable, It´s a Trap). And with Lumi gone, there isn't another leader skill that is at all worth it. Leia could give herself and AA crit chance (and eventually Lando, if he goes into the team without replacing Leia), but RG, GS and Rey don't have leader skills.
The reason I like AA with Rey, is that Tactical Genius allows Rey to Leverage and Flurry in a single turn. I wish AA was faster so he could go before Rey, but getting a regular attack in on the first turn and ohko'ing someone in the second turn is usually okay. Especially as it heals her if she got attacked at all. Add the minor synergy between AA's dispell and Rey's Focused Strikes and I like the core of AA+Leia+Rey. RG is currently far and away my best tank (I have a 3* shore trooper which isn't geared at all, and I have a 2* scariff pathfinder, also completely ungeared), so he goes in the team too, leaving the final slot to play around with. I have Old Daka, GS and Lumi at a level where they are playable, but none have true synergy with the first 3. Lando seems the best fit, but still gearing him, and he is also only at 4* (Cantina farm is a long slow grind), I could also put in QGJ (also undergeared and understarred).
Anyway, I took the initial advice and got AA to gear VII. The next Holo Projector and Droid Caller will go to RG, but to get him to gear VIII, I'll also need another 41 pieces of Sensor Array salvage. Quite the farm :/