Dancer Tank!!!

[Leogun]

Only it's really not. Only cartoons and comic books refer to combat as similar to dancing, and their comparisons are usually flawed. Real fighting is much different. You have an opponent, not a partner. You're not working in synchronicity and harmony with one another, you're actively trying to disrupt one another to gain positional advantage using maneuver. Even the flashier styles of combat that look more elegant to the eye have very few similarities to dancing.

I said figuratively, which can be finding similarities between the two. Take a simple Bruce Lee quote:

"Absorb what is useful, discard what is not. Add what is uniquely your own."

Since dancing and fighting tend to take the direction of styles, it's not farfetched to bridge the concept of developing your own style to suit yourself or the situation.

That being said, please don't try to separate flashy movies and cartoons from another entertainment media (video games). I shouldn't have to remind you we're talking about video games so if you've seen or heard it described as dancing in an anime or movie, guess what? A video game is within poking distance of the same concept

There are a lot of cultures which traditionally incorporated dancing into their ceremonies for this very reason (proper dancing, not some hack tv competition). The idea is to let the elegance of the dance sooth your soul (similar to the feeling people get when they watch an emotional Balet. Even if it's a tragedy, it's often described as being emotionally liberating). It still doesn't really fit in a combat situation, but it sounds a lot more related to healing than tanking to me. I suppose you could make the argument that the Dancer would be enchanting the mobs in a similar way ... but unless the goal has changed to wanting to sooth their anger and send them all home happy and content, I don't think Dancing really fits.

PS: I think this concept is covered by Bard, evoking emotions through music. Dancing, as you mention, really doesn't fit a combat situation so how would it heal? You have to SEE the dance for it to effect you, right? So taking your eyes off the enemy? Bad idea. Unless we're talking about some other effect (i.e. the dancing creating an effect which then influence those around them similar to a rain dance summoning a rain storm)...

I could see Dancer working in various concepts with specific conceptual directions, be it healer, DPS or tank. I just think tank would work best for the pure dance theme since it could be about dancing out of harms way or distracting foes with your movements. Every other concept likely has some pseudo-magic effect for it to rely on.