Grievous. Absolutely Grievous.
Grievous is a Magikarp. You basically don't have him right now. Most characters are only moderately less effective at G11. Not Grievous. Even with that zeta, he's a load without more gear.
Maxed Grievous has 58863 max HP. 38950 of that comes from G12 pieces. That's two thirds of his health. And that HP from G12 pieces is not subject to mods until you get to G13. Unless you get him to G12 with at least some of those pieces slotted, he will not help you.
The main strategy is Grievous and Asajj ramping their damage and dealing out big hits as the less important allies die, but that requires them to be monsters.
Other than that? B2 is the Dengar of this mission. Gear helps it survive, though mostly it's there to clear buffs and apply buff block, with a side of being eaten by Grievous to scale his max HP. Magnaguard sucks to gear, but you want it to tank enough hits for GG to get a nibble or two out of it before dying. Then I'd say Nute Gunray, with zetas on B2 and Nute. This turns B2 with his debuffs into both a noticeable damage and TM source. Also, Nute can die twice, giving Grievous two bonus turns.
