That's not how it works.
Zed can stay far back and farm safely and engage from that range, being the only assassin able to do so without sacrificing anything, has last hit assistant and no longer even needs to hit his Q to kill most of the time.
Why do I say he's the only one?
Talon - Can stay back and farm with W, but then unless you walk up to him, he can't engage on you.
LeBlanc - Can stay back and try to farm safely, but again, unless you walk up to her, she can't reach you.
Ekko - See above
Fizz - Either stays back and tries to farm under tower taking harass, or loses farm to stay safe
Akali - Same as Fizz, just has a bit of an easier time due to safety to compensate for her having the lowest TTK of all assassins and her sever energy cost on Q, tho her healing only works if she has at least 180 energy and energy regenerates at a rate of 10/s with Q early costing 100 energy.
Then there's Zed. Can harass you from over 1000 range, is safe a f with his W and Q's range, can easily farm with Q that has basically no cost, and his WR engage allows him to engage on you from the other side of the map. Let's not even talk about the fact that he has a last hit assistant for no reason, and being an AD champ, has access to the most broken items in the game.
Where is the high risk in that?
Also, AD champs can buy Executioner's Calling for 800 gold, screwing her healing and all mages have good CC to keep her at bay if she tries to be funny and dive.