You seem under the impression I'm saying Zoro is more important in Wano, and it's more his arc, because he's fighting Kaido.
Let's be clear, that is the furthest thing from what I'm saying.
Zoro, even if he never even sees Kaido, is more important to the arc than Kid and Law. There is far more to the story than being Luffy's backup in a fight.
It just so happens that, given Zoro's carrying around Oden's sword and used to carry around Ryuma sword, yes, there's reason to think that like them he's going to have a fight with a dragon on Wano.
Comparing Wano to Dressrosa is pointless. There, the situations were reversed. Law clearly had more build up with Doflamingo than Zoro did. Zoro was a comparatively bit part player in that arc, he got his usual fight with the strongest subordinate, and he got some setup for the future by hanging around with the Red Scabbards (another big Wano alert) and Fujitora. Whereas Law was at the heart of the fight with Doflamingo- his history with him was the catalyst for the arc.
Since then, though, Law's importance has waned. He's here because the story needs him still to be kicking around, but the heart of his plot was the conflict with Doflamingo, and that's done now.
Kid's importance in on the rise, but his grudge with Kaido is seriously lacking. He's angry with him cause... Kaido beat him up and gave Killer a SMILE. That's it. He's a side player to the main conflict of Luffy, Zoro and the Scabbards vs Kaido and Orochi. We expect him to have a decent enough role in the finale because he hasn't actually done anything yet, but that's about it for him. I'd actually argue that we should be expecting more from Kid if we ever get to see him in an arc with Shanks, because there's more narrative set up for that to be important to Kid. It was the Red Hairs that cut off his arm, it was Shanks he was aiming to defeat. Plus they're from the same sea. There's an actual story there that's very lacking with Kid's involvement in the Wano arc.