Only reason for domino would be it you haven’t finished act 5 and have rulk and massacre for stomping through content, magneto is high utility counter for anything with metal tag, when doing content (not arena) parry and use long heavies to gain lots of prowess charges, keep doing that until special 3 and unleash, should be on 40ish prowess if you are holding heavy down for a while before releasing, even against non metal he’s very powerful using parry heavy s3, and he doesn’t need two synergy partners to produce the damage, I still use domino a lot, for stomping through all the uncollected eq and easy paths, with that synergy she’s great at destroying easy content, but magneto is a counter for a lot of harder content where the opponents have metal tag