It's a solid bard class with focus on the Battledance, empowering extra attacks as you move around th--okay, it's basically the Dervish, I've totally converted this one too, but for Fighter. This is a good progression for the Bard class, though. The added adventure hooks and stat block for a dancer are fun and creative, a nice added bonus.
There's nothing explicitly bad, here. If there's anything I'm disappointed by, it's exclusive focus on combat attacks and combat statistics. I think this class could get away with a different level 6 or level 14 feature that focuses more on Charisma (Performance) or some other RP-focused aspect of a dancer.
In any case, it's a nice bard subclass!