I agree that Zed could use a rework(He's either extremely oppressive, or damn near useless).
And certainly wasn't saying that he gets to easily cut through the defense <3 It's just impractical for most midlaners to build more armor than Zhonyas or Guardian Angel, plus Tabi, without really hindering their build. His core build provides enough to negate a decent chunk of that armor(Not all by any means), leaving the average midlaner with no other "Viable" options for armor items to build. Doesn't apply to every champ by any means, but the average pick in mid needs to focus on damage items or they're more useless than the Zed that can't kill them is.
IMO the biggest Zed problem is that even when he's useless, he feels oppressive. His Trading pattern is extremely non-interactive in general - He stands as far away as he can, hits you with Q's from his shadow(And ideally his own Q/Shadow's E as well), and eventually procs the second part of his W to get into range when he can kill you. His "trading" pattern doesn't allow for much in the way of actually trading with him, unless he tries to all in you. If he's not miles behind and useless, he can just run at you and dump everything on you to kill you - Still allowing very little meaningful options to do much in return for many champions.
Making him have to actually put himself at risk(A little more often) in order to trade and chunk his opponents down would, In my opinion, allow for him to potentially be buffed significantly in other ways, without him feeling so oppressive for his opponents.
Personally I don't have much trouble with him usually - Like you said, grab a seekers and Tabis and he's done(As long as he isn't already fed), But he DOES feel extremely frustrating to lane against if I'm not playing a champion that can just ignore his poke, as there's not a whole lot of opportunity to respond to a decent Zed who doesn't come into range until he can R and kill you.
Just my opinion <3 In the end I hope he gets to a point where his mains are happy with him, and his opponents aren't oppressed by him.