Is Kassadin in a Viable state for buffs?

Just curious on how other people currently feel about Kassadin, do you think he's OP, great, good, ok, or bad?

I personally have 29 games on him this season with a really good 72% Winrate, but I still think he could use some more minor side buffs, increase damage on E by 20 at all ranks, or increase base MS to 345, reduce Riftwalk stack duration back down to 12, increase Riftwalk range to around 550-575, rebuff W base damage to 180 max rank. Idk these are just a couple of thoughts I've had over the past couple of days.

Let me know what you guys think.