Marie is okay. She's looking to be a solid mid-tier character, but has nothing that would make her top tier. Her weather system if mastered I think can make her somewhat difficult to fight, but the drawback is that as a Marie player you'll need some foresight, since changing the weather costs 50 SP, and the weather changes randomly at the start of each match.

And any amount of lag is bad for Yosuke anyways, like, ANY amount. He can't even really deal with just a little bit.