Darth Revan and then Malak

For Darth Revan, G10 or so is probably fine. You might suffer at the hands of RNGesus a bit on tier 5. I went on tilt and rage-zeta'd Carth before I figured out a strategy that worked, but I still use my OR squad in grand arena so it's not a big deal.

For Malak, as others have said, you pretty much need to G12 most characters to get them over the threshold if they aren't zeta'd. Might need to slice a mod or two to 6E as well. Dark Bastila and anyone else with more than 4 abilities (can't remember them all offhand) are a bit easier. You'll want your light side team to be as diesel as you can make them though, because it's really hard. Dark side is stupid easy so whatever you need to hit the minimum is fine.