First of all I don't fight for now for top rank, I stay top 100 usually 40-60.
Galactic Republic is my main squad there, and I've now integrated Anakin's ship as reinforcement instead of JC's ship (all abilities maxed and JC gr XII). Anakin's ship has its abilities lvl 7 only and 3*, reinforcement ability lvl 2 (so no expose when he reinforces).
My line up is Biggs, Vader, Fives with reinforcements Ahsoka, Plo Koon, Sarge and now Anakin. I can say that since he's on my team, it's easier to win most of the battles. He gives GR ships a good boost on offense, and imo he must be used as reinforcement since he then provides offense up and especially accuracy up.
Accuracy up really helps in my battle since there's a lot of Imp TIE fighters. Battle that I could lost with its evasion are now easier to win since he cannot evade anymore with this buff.
Usually, I can win a battle before the insta-kill of Thrawn and if not, Sarge dies but the other ones can win thanks to the Protection Up given by Convergence.
Hardest for me are still the geos with Ackbar.