excuse me
but did you just say that assassin's fall off late game?
because if you are serious about this then i must point out that all assassins have a very strong late game and a weak early game
why do you think all people say, "Shut them down early so they can't do anything late game"
and if that tip that all high elo players say to bronze people(im a bronzie and am told this alot) then let me gives you some examples.
No one is going to die to leblanc 20 minutes in and say it's ok cause she won't hurt me after the 30 minute mark
plus zed's build doesn't even give him that much attack damage
his biggest ad item is hydra which is 75 damage
and if the ad bonus was removed
zed would have to either get a massive buff to his r or his e or his passive
IMO zed is balanced and very easy to play against
try picking someone like lissandra or ahri against zed
lissandra can take out his mobility if he goes in on her
and ahri can spirit rush to escape his ult and should be able to have a 100% chance to hit him with charm because his ult pretty much shows you where he will be in the next second