A buddy of mine in my shard (day one shard) cashes at number one every day and typically doesn't drop much in the rankings. In the past week I have yet to see him drop below 15. He runs the following:
DN - Leader
Sith Trooper
Sith Assassin
GK
Thawn
All are 7* G11 with the exception of Thawn who is 6* G9. Thawn has zeta on unique. It also doesn't hurt that DN is modded to 220 speed and SA at 266 speed.
Regardless, this team is scary. Still beatable with some good RNG but I have yet to see a better team with Thrawn.