I shared the same sentiments about them a few weeks ago, until I have actually brought and tried out Zed and Fizz.
To begin with, Zed isn't that much of an offender. He needs to build for his damage, which becomes moot if he falls behind. Additionally, he does not have any sort of hard CC by himself; if he does not kill you with death mark, you can probably get away.
I believe the main source of his power is that he synthesizes very well with items that cover for the weaknesses in his kit. BoTRK gives him higher alpha damge and a much needed slow to catch escaping enemies without burning shadow slash. Ghost Blade as well has the same cool down as death mark, further increasing the kill potential when he ults. Furthermore, item effects and ignite add to the damage when death mark triggers.
To compensate for this boon, there are Zhonyas and QSS to counter his ult, assuming that you can survive a regular rotation. He definitely is on the strong side as of now, but there are so many champions that has essentially built-in counters in their kits such as Kayle or Akali that Zed does not warrant a nerf.
The same cannot be said for Fizz on the other hand. When I first tried him, I was disgusted by how much his scale scales. With Lich Bane proc and Sea Stone Trident, one Q basically deals 300% of your AP damage. Additionally, Playful/Trickster is on a 5 second CD with full CDR while simultaneously offer great AP ratios, and a 800 unit dash or a 60% slow. He has another AOE nuke with his ult, not to mention that he essentially has a free Doran shield passive as his passive against ranged during laning phrase.
Worst of all though, is that Fizz can get a Zhonyas as well. Whats the point of putting in a balancing element if the champion it is suppose to be used against can use it as well?
If Riot were to nerf Zed, they better do so with Fizz as well.
