I played the Mystic class, briefly. I made a martial-focused build, and the DPR was very close to Warlocks and Paladins. The nova abilities were effective but expensive, comparable to smites. Using psi points to put the exact amount of oomph I wanted into an ability was a ton of fun and turned into a threat-analysis minigame -- very thematic for an intelligence caster.

Where the Mystic went nuts was the infinite toolbelt. The best way to explain this is through raw numbers. A level 5 Wizard -- the de facto swiss army knife of D&D -- can have 4 cantrips and 9 spells prepared, plus 1-2 freebie abilities. A level 5 Mystic could have 2 talents, 5 disciplines (each with about 4 active options and 1 focus), plus 1-3 freebies.

In other words, a Mystic could have 30 abilities to a Wizard's 15. And it shows. While playing, I quickly realized that I had a solution to every single situation. And as fun as it is to be the guy with the shark repellent spray, it's pretty obviously bad game design.

I think ultimately what I really wanted was an intelligence-based Paladin.