Vergil + Morrigan is the sugar mama combination. Paired with a decent beam assist, things get stupid quick between Vergil's increasing threat level the more meter he has stocked and quick beams allowing him to start left-rights with teleport and assist. SRK's Vergil/Morrigan/Doom is a pretty cool team for this. Magnus with Estaka on anchor seems stronger to me though.
Also, I find it hilarious that people are messing with meter assist theory craft now. I wish I had some of my old conversations with Sixfortyfive on hand from the old Marvel threads. And yeah, Morrigan isn't high tier, just a solid low to mid A.
Edit: Dr. Strange is a hard Morrigan counter.
do you really need a beam for Vergil mixups? With the meter dump he'll get out of morrigan/doom keepaway he'll be able to do all kinds of stuff with swords and keeping people pinned down with missiles