Fizz needs something taken out of his kit.
He simply brings too much to the table. A gap closer/escape that can be cast twice, slows, and damages. Another gap closer on his q, DOT, and reduced healing on his W, which hurts the more you attack them. A passive that lets him take less basic attack damage, and ignore unit collision, and an ult that slows and knocks up.
Personally I'd say either take out his damage on his e OR remove the slow, maybe also keep turret aggro if he playfuls. Another option would be to remove the DOT on his W.
Maybe these ideas are awful, but for me there are only a handful of champions that are a must ban EVERY game, no matter what the team, and he's one of them. He's simply too slippery for the amount of damage he puts out. If anyone has any better suggestions I'd love to hear them, or at least create a discussion and explain to me how I'm wrong and he's fine as he is.