Maokai: infinite sustain, unreal base attack speed, every ability nukes, has aoe percent damage reduction that also absorbs damage to nuke you with, has freaking untargetability, percent max hp damage, a targeted gapcloser, and a knockback.
I mean, holy wtf overloaded kit!? Maokai must be the most overloaded champion in the game.
Seriously though, you can make this argument about anyone. If you just list kit elements, you can make almost anyone sounds overloaded or OP. I
And seriously, if you are going to use that argument, pick someone other than Maokai. Maokai does most things well nowadays. He deals with all situations quite well. That's something I'd call overloaded much more readily than I would call Darius' kit overloaded.
Darius nukes at close range, and is worthless outside of it. His close range prowess is not due to any specific mechanics. It is due to numbers. Numerically, no one can outtrade him. The only differentiating mechanics he has are the ult and the pull, and that is not enough for me to call him overloaded. He does 1-2 things well and fails at most other things. That lack of potential is not what being overloaded is. Thresh and Yasuo are overloaded because when they are strong, they are the best at almost everything. Darius has many things he is terrible at, no matter how strong he is. His weaknesses are not lowered or mediated by any part of his kit.
Zyra has skillshot nukes and some CC. It's the same as Lux, Ori, or any other utility mage. There is nothing significant differentiating her from any of them. The turrets mean pretty much nothing different from any standard nuke. You use them in exactly the same way and they do exactly the same thing as any other nuke. That's not overloaded, it's a different way of doing the exact same thing. Overloaded means you have more options, not the same option wearing a slightly different hat.
CertainlyT has produced a few overloaded champions for sure. Zyra and Darius are not among them.