I feel like the only reason Killer was on the rooftop was so that it didn't look weird that Oda put Zoro there lol
If anything this just goes to show that the whole rivalry portrayal shit barely means anything when it comes to power-scaling. Because by the time of the rooftop fight Zoro already proved his superiority over Killer and now it's just overkill. Sanji is stronger than him now too.
Even with Kid and Law, no matter how much Oda plays up the dynamic of the two of them being Luffy's rivals, he just outclasses them