Dancer was just the result of explosive amounts of fan speculation around the lady in red. She's very likely just a fancy monk, but her costume and fluid movements at the trailer's start had people literally shouting "Dancer! Dancer confirmed!" less than a minute into it, only to see her then go into a matial arts sparring match with Derplander seconds later.
It doesn't help that the Vegas fest was really weak on actual announcements. All the hype and build up, only to have so little to chew on afterwords that the dancer speculation just became the hot topic.
We had already talked about Red Mage for so long, I guess it was less a "Woo! Comfirmed!" and more of an "About time you add it!"
