That's true, he won't get that level of importance as he isn't a major enemy. But that doesn't necessarily have to take away anything from his strength. I really don't think Oda is done with him yet and that he 'isn't worth anybody's time' who's on the rooftop.
Probably. But one thing that'll always stop me from placing Zoro above Luffy is that I don't see Zoro following someone who's weaker than him. Like never. Even in FI, Zoro himself said that Luffy needed to step down as captain if he didn't at least have CoC.