Unfortunately, this thread contains so much hyperbole that it is difficult for me to find anything to respond to. If you would like to have a rational discussion about Zed, I'm up for it, but please avoid statements like "If one enemy has QSS, Zed is useless" (there are other targets and you can wait until QSS is down -- it's called counterplay) or "I can't damage a person who starts cloth 5" (you yourself can open all consumables + ward and are manaless).
Since I'm not going to go into a detailed response here, I can give you a few pieces of context from my end:
*Zed's winrate (like most assassins) goes up with game length -- the longer the game, the more impactful he becomes;
*LoLKing data is highly inaccurate -- it's a fun site, but please do not quote it as evidence for Zed's power level (in either direction, it's entirely possible for a champion to show at 53% on LoLKing and be fine or weak);
*Zed has a very high mastery cap, perhaps the highest of any champion in our roster. It's easy to become frustrated if you play Zed and do not always see the success you do with other champions. If that is your personality type, you probably shouldn't play Zed. He is designed for a player that is interested in learning new strategies even on game 100, even if that means leaving a majority of fights thinking "I could have played that better;"
*We are at a pretty tanky point in the meta at the moment. There are a lot of times in draft where I look at the enemy team and think "this is not a good game for me to play Zed." To my eye, this isn't a bad thing. All champions, and assassins in particular, will fluctuate in success rate as the meta turns. One could argue that Zed's current level of success in a heavily defensive meta is probably a sign that he is over-tuned. I am more inclined to think that Live Design got his sustained damage values about right prior to release, but your interpretation may vary.
*The PBE re-distribution of power from Zed's E to Q is an attempt to make the choice between what to rank first (Q or E) and second (W or the other of QE) more meaningful. Flexibility is a form of power, in that it gives the player greater ability to adapt to their opponent's strategy. It's far from final, but I think the change is directionally sound, even if the numbers aren't quite tuned yet. For reference, a large number of our Live designers play Zed proficiently -- JHa, SmashGizmo, Scarizard (to the extent he can be called proficient at LoL), and RiotMilkCow -- so we are in good hands.