Its level 1-10 power curve is too steep, like a combo melee+caster; then its 11-20 power curve flattens, like a melee.
(Here, "melee" I mean "uses weapons for combat power", and "caster" I mean "uses spellcasting engine for combat power").
Psychic Focus is a floating decent feature, plus a channel-divinity thing.
Psi Points, at lower levels, is full caster spell points.
Then you have features like Mystical Recovery / Consumptive Power / Telepathy / etc. Which are solid.
Then you look at each discipline. Each of them is about half to 1/3 of a class's worth of abilities, and you have 5 of them by level 5.
While someone else needs to Paladin 2 to get smite, you just burn one of your 5 disciplines and and get psychic smite that is 80% as good. Or get a discipline that, starting at level 9, lets you cast a 5th level spell to let almost all of your allies make a full attack.
Post 10, what you get is overlapping concentration as a replacement for 6th+ level spells. So no new mechanics. So in the back 10 (L 11-20), while you start from a high point (with like 3 classes worth of features welded together, all level 10), you don't scale like a full caster after it.
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Design wise, the problem with the super-scaling abilities is that they lack some of the twists of spells.
Like, fireball -- great damage spell, often annoying to use. Your alternative is scorching ray, which does less damage often even on a single target, so sometimes you'll use it when it isn't optimal.
With a Mystic, this only happens if the Mystic didn't pick the other option. The damage abilities all scale per point spent.
They scale a bit too fast and stack too much.
As an example, inflict wounds does 2d10+1d10 per spell level. Beastial claws does 1d10 per PP. At level 1, wounds is 3d10 vs 1d10.
At level 1 it is 3d10 vs 2d10
At level 3 it is 4d10 vs 3d10
At level 5 it is 5d10 vs 5d10
At level 7 it is 6d10 vs 6d10
At level 9 it is 7d10 vs 7d10.
Looks fine, right?
Then you break it. You use a bonus action to Brute Strike (+1d6 per PP) before attacking, and on a hit also burn Knock back (+1d6 per PP).
Your tap is now 12.5 damage for 3 PP.
L 3: 37.5
L5: 62.5
L7: 75
L9: 87.5
And maybe you mix in another 1d8 by using the animate weapon instead of claws (1d8 damage class feature), and you have giant growth up for +2d6 per swing.
So at level 9 you can make a 99 damage strike.
And that wasn't me looking up broken combos, but just doing a quick "how hard can you hit with these abilities" while writing this post.
Now you did burn a lot of PP to do this. But you also have efficient options beyond this kind of nova.
