Well with Azure Fang's "Regenerative Healing Jutsu", they're usually buffed up to where they can heal just as much, if not more, than a 4-5*Sakura's healing.
As for Breeze Dancer, "Dance of Impertus" is really only used in order to use Sage Naruto's "True Wind Style - Rasen Shuriken" 2 rounds in a row... Which is even more powerful since he's usually buffed up so much. And, even if Sage Naruto couldn't generate 20 extra Chakra points a round, he would still be able to use his Mystery 2 rounds in a row thanks to Breeze Dancer's "Dance of Impertus". And yes, there are measures to counter this, but it's extremely difficult to do so during Ranked and Space-Time battle since it's auto.
As for Breeze Dancer (and Azure Fang) being one of the least used classes, I have to disagree with that. In fact, I've seen Azure Fangs used more than any other class due to that cheap Mabui - GNW Tenten - Mei (or Darui) line-up.
I'm not saying that what their Mysteries do should be changed; just have them cost 20 measly Chakra points is all. That seems fair.