Bruh... I'll try to explain why you are having trouble seeing it my way.
She has that haki and iron bulls running at her are getting clean hits in...
You can counter that but that's only because she was affected by Law's cheap shot.
It is not because of that, she wasnt affected by it when Franky's Rhino bike rammed into her face head-on.
She wasnt affected by that when Zoro snatched Prometheus from under her and she fell into the dirt face down...
Kaido has the same haki and even he couldnt stop CoC-less Zoro from slashing his chest open. And he tried.
Hommies arent a problem for Law and Kidd, I dont know why someone far superior would have a problem with them...
Stamina is not a problem for Zoro, Big Mom is in a problem because no way she can last against Zoro with such bad performance.
The part where I agree is that top tiers shouldnt be mid diffed from a story writing perspective since it makes the whole tier look bad.
However, it already basically happened with King. You may not consider him top tier but he undoubtedly is one.
You have two voices in your head, one that you would describe as reasonable and the other you would call unreasonable.
"Reasonable" one says Zoro cant be that strong. "Unreasonable" one asks What if he is that strong.
One thing is always true with Zoro - he surpasses all expectations.