Thinking about Psionic Mastery, one of the issues I saw is that many effects have their cost limited to 7 points. Another thing that mastery could have is some sort of "metamagic" like extra to apply disciplines, like more targets or greater area of effect.
To me, Psionic Mastery seems to be all about doing your own custom mental stunt. I does not need metamagic-like extras, as Psionic Mastery is already a mix of quicken and something else that allows for multiple concentration.
I really like that psionic powers were restricted to the equivalent of 5th level spells, as the greatest psionic powers of old were limited in effect to something similar to that. And it is refreshing to see a different path to achieve effects adequate for the higher levels of gameplay, with customizable packages of lower power effects. Moreover, I am not sure how is it relevant for Psionic Mastery that some psionic effects are limited to 7 points, when the mystic can simply activate multiple damaging powers at once and just focus fire, if all one really cares is do a lot of damage.
Anyhow, the mystic does not seem to me a very efficient damage dealer overall, which is something I like. Surely they can go nova for some impressive single target stunts, but they don't seem to actually perform better than other nova-builds already available, and to even reach this higher nova potential, it is just too many power points wasted, as the individual powers are quite underwhelming, cost-to-damage wise. The mystic will perform better throughout the adventuring day by going a little slower in pace, doing a lot of tactical stuff, locking down single powerful individuals, messing up with enemies minds, playing with positioning and battlefield control through telekinesis, all that fun stuff.
As a side note, the capacity to absorb damage from a immortal is really impressive. Also, their penchant for self-sufficiency is a nice touch. The fact that the are MAD seems to be on purpose, so to give the player interesting choices about focusing on offense, defense or a more balanced build.