The UA mystic class was discontinued due to poor playtest response. It was a rough concept from the beginning, and while I respect WotC's decision to bin the class in favor of subclass options... I think it is still possible to succeed where they have failed.
This revision of the mystic class is designed to keep the same feeling and theme as the original intended, and attempts to keep true to the implementation of psychic/psionic abilities in past editions of the game.
While much of the feeling was preserved, many of the mechanics have been altered or replaced in favor of a newer and lighter system of psionic abilities and subclasses.
And lastly, this homebrew class is a living concept. By using this class and participating with feedback on how it fares in games you can help improve and refine it into a better balanced and functional class. I do not intend to let this content stagnate, and with your help I hope to make it as viable as any other official class in the game.
- from the publisher's blurb