The thing with Zed is that he is not really an all-in type of Assassin until he has gotten a few items, most of his snowballing potential is dependant on weakening his opponents with his combo until they're at a low enough point for him to swoop in and finish them off. Zed provides only damage with no utility beyond a slow, he has a very dominant laning phase because that is how he keeps himself relevant and strong.
I don't deny that fighting Zed is extremely frustrating, but that is just the way the cookie crumbles. If we went by your example then that would not only reduce his damage to champions and reliability with hitting his Q, but it would also adversely affect his farming and last-hitting potential significantly. There's a lot of champions which I deem to be cancerous, and would absolutely love to see removed from the game completely, such as Yasuo. But that doesn't mean I think he needs a nerf.
Zed is designed to weaken you, and then destroy you when you're too wounded to fight back. To do that he needs to have very strong and consistent harass.