No, it's absolutely important to break up Jase/Scott if they want to crack the 4H. If Marvin goes, the remaining 4H are rock-solid, and then it's down to who's HOH, which (if past comps are any indication) will more likely than not be a 4H. If Scott goes, Marvin is a lot less solid in that alliance than Scott, so it's weakened. Not to mention that Scott directly controls Cowboy, so his loss will shake CB up and take him out of the game for the HOH competition. Marvin is not dependable for their side, but Scott is ABSOLUTELY UNRELIABLE for their side.
Once in the house, I think A and Nat will stick with the Girl Power group, but it's an open question as to whether the GPG will stick with them. They need to, because Nat is one extra number for them (which, although they don't know it now, could give them a second bite at the 4H if they were silly enough to vote out Marvin).