Not sure what level you currently are but for now I'd probably go with Barriss Offee (L), Darth Maul, Ima-Gun Di, Asajj Ventress, and Count Dooku.
Why? Mainly because they're your highest star characters.
But in addition to that, Barriss is a strong healer and with a leader ability that gives everyone extra health. Her heal is able to ignore any healing immunity debuffs as well. Dooku has a 100% counter ability with bonus attacks. Maul and Asajj are fairly decent damage dealers.
You could also go with an all Jedi counter team consisting of: Ima-Gun Di (L), Barriss Offee, Ahsoka Tano, Kit Fisto, and Jedi Consular.
But the only downside is Kit Fisto and Consular are only 2* and would be fairly weak.
