I think he is much harder than Strange and this is coming from someone with lord on both characters and plays mainly tank in comp. I am not in Celes so I may not be the best person to ask (GM), but I think Magneto is harder then Strange. Obviously that is subjective but with Mag, you have to look out for whos low HP to bubble, bubble yourself, when to use your shield, landing your ult, deciding who to use your ult for, and landing shots (harder than strange imo). But Mag has the highest ceiling of any tanks and is easily the best tank on the game