Is it just me or FIzz's W DOT too strong?

Every single game I've played vs a FIzz top ( or played as a Fizz top), I notice that no matter how much i screw up trades ( taking minion aggro, not procing grasp), the longer the trade goes the more it goes in my favor.

I've looked it up on the wiki and i noticed that the DOT is on his passive, meaning it's not even as simple as "Oh, just wait for his W passive to expire", since just 1 auto procs it again.

This reminded me of another champion that has a similar %hp missing damage skill, the infamous @ 57% winrate.

Now, I get that Fizz is to be played as an Ap Burst Mid with his W used to secure kills, but what i don't understand is why he has %hp damage. %hp is normally only made for tanks, and fizz wasn't intended to be a tank. Shoving FIzz into his tower forces him to use his w active to cs , but the active part of his w is very weak unless building ap, so he's never really punished for caressly spamming w ( that thing only has a 4 second window downtime too btw)

tldr: It's impossible to punish tank fizz in lane since his W passive makes almost all trades go in his favor. Move the %missing damage to his active plz