I'd argue that in pure blade handling skills, Killer B is among the most impressive out there. His unique fighting style incorporating advanced acrobatics while handling 8 blades simultaneously is simply a marvel to behold visually.
It's also potent enough to completely overwhelm a skilled sword user like Sasuke, who also possesses the Sharingan with its kinetic vision that can keep up with fast moving objects, analyze their trajectories even if they're faster than the user, and analyze objects on the cellular level or smaller. In addition to its Analytical prediction that allows the user to visually see the opponent's next move. In fact, it was even mentioned that Sasuke couldn't predict B's movement at all, and this wasn't some bs resistance, it was simply due to his skill and unpredictability. (Wasn't due to speed either, since Sasuke could react to a much faster B when he wasn't utilizing his sword style)
I'm not trying to argue that B should be higher or anything, as I'm not too knowledgeable on the other characters on that list aside from Zoro, Mihawk, and Musashi (Fate). All I'm saying is that B definitely belongs on this list, and I wanted to put his pure swordsmanship and blade handling into perspective.
I mean, EIGHT ******* BLADES! Who can do that?!
Anyway, here's a glimpse for those unfamiliar with the character: