Depends what you mean by "beat gc". Beat any individual battle? Get you red crate? What level?
On hard no single team can possibly get you red crate. You need the feats which require all sorts of comps, mostly scoundrels this time.
Some GL teams can't beat every team they find in gc. Especially with stamina drain.
Loads of feats in the last 5 conquests have been easily completed by a CLS team. The higher relic you have the lower stamina they can work at. Han shooting first is handy all over the place.
I don't have a useful sith empire team for conquest, so can't really advise on this. Except for my r5 Malak that sees quite a bit of use. He is a useful tank all over the game. As the team inflicts a lot of debuffs I imagine they do quite well with a lot of the data disks that interact with numbers of debuffs or do bonus damage along with debuffs. But they rely on drevan outspeeding opponents so they will get blown away after sector 3, if not before.