The problem I see, though, is that if you eventually start nerfing/changing him around so much that he's balanced on Dominion (which is great), he might end up being complete trash in SR...and let's face it, he's a pretty crummy pick on SR currently.

How about lowering this Riftwalk range so he can't flash over walls that shouldn't be allowed to flash over.

I think the problem is both the cooldown and the range on riftwalk.

Riftwalk gets to about 3 seconds with max cdr, and can go over pretty much every single wall in Dominion.

Nerfing the range to about 700-800 shouldn't impact him too badly in SR, and increasing the cooldown by at least 3-5 seconds wouldn't be too bad either, but it would make it so that if you blink into a stupid situation you're stuck with your bad decision.

Nerf, disable, delete Kassadin. Fix this issue.

As an AP caster , i have to admit Kassadin is the only AP assassin i worry about in the loading screen. Especially when its a Kass+Talon on the enemy team, i usually have a rough time assuming they're decent. But i've learned to deal with him and i think its sad that people have to play Kassadin to get higher elo ,which is what i keep hearing. I've played him twice on dom in a real game and once versus my friend (1v1) and i have to admit hes pretty faceroll especially when your used to playing AP champs that actually take some effort like Ori, Ahri , Cassio , etc. As of now i have refused to play Kass cuz i want to continue playing and getting Really good at the Casters that are great for a team like Zyra. This might sound stupid but i actually don't think Kassadin should be nerfed Please dont hate me lol