Movement speed buff on Kassadin?

I think Kassadin is better now and almost in a good spot, his winrate is still very low (41-42%) but he's not trash anymore.

What I do think he needs is a slight MS buff, maybe to 345 or 350 (probably the former). I think this change will be enough to put him as a mid tier pick without making him OP. He still struggles with escaping people with insane MS especially pre-16 when Riftwalk still has relatively long cooldown. I don't think this will make him more mobile then before (700 range compared to 500 is still huge) but it should be a nice change.

As for why he should be fast? He fucking floats, Lee Sin can't do that