Sunday we wrapped up a 5 game set in Eberron that went from Level 1 to 11. I played a Mystic using WotC's playtest rules put out in 2017.
https://media.wizards.com/2017/dnd/downloads/UAMystic3.pdf
While 1 to 11th is technically only "half the levels", it covers the half that the vast majority of campaigns actually run in, so I think I gave the class a pretty good test run. I selected the Order of the Awakened as my subclass. By the time I retired the character at 11th level he had the following Talents/Disciplines
Talents
Mind Thrust
Mystic Hand
Mind Slam (Not sure I ever actually used this one as I didn't take it until level 10.)
Disciplines
Aura Sight
Mastery of Ice
Mastery of Water
Nomadic Step
Psionic Restoration
Psychic Assualt
Telepathic Contact
Note that I used the ability to switch out a Discipline upon level up liberally in early levels, so at various points in the campaign I tried out Mastery of Force and Psychic Disruption.
Overall, my DM declared that the Mystic was "Tier A, but not quite overpowered." I think I'd agree with that assessement.
One of the most powerful abilities the Mystic has is the ability to target Intelligence saves. Mind Thrust was my bread and butter early on, Psychic Assault came into its own with Ego Whip (a single target shutdown) and later Psychic Crush, and then the Telepathic Contact Discipline with a chain of Int-save based Paralyze or Dominate effects. Intelligence saves rather than Wisdom saves are so important because non-sapient monsters are going to be rolling with a -3 to their Int save, and there are a lot of big powerful, but non-sapient monsters in the DMG. Granted that might change from levels 11+ as non-intelligent monsters get thinner on the ground, but see my remark about where most campaigns spent their time.
The other ability I really have to single out is the Nomadic Step Discipline from Level 7 onwards.
Yes, you never get the world-hopping ability of an Arcane caster's teleport circle, which is why the class is not quite overpowered, but Phantom Caravan is crazy. My character was able to grant the whole party enormous tactical flexibility and emergency escape whenever we needed it. We'd zip past obstacles, outpace enemies, and appear behind enemy lines. These are expensive powers, sure, so I couldn't just use them all the time, but there so many occasions when it came in handy:
Anyway, my understanding is that they're going to rewrite the whole Mystic pretty much from scratch, but it was definitely an interesting experience to play one. Careful power selection was able to cover for a lot of the class's weaknesses, but the power points led to a tendency to Nova that had to be carefully managed. The free Telepathy was all right too; even if the other PCs couldn't talk back I was able to give them information effectively on a number of locations.
Addendum: As far as Eberron-specific stuff, I took the "Aberrant Dragonmark" feat and eventually met up with the Aberrant refugee "House" in Sharn. Since my conceit was that my character's psionic abilities were being powered by his Aberrant mark, I started to train the other Aberrant Marked in how to use their own marks to power psionics and ended the campaign as basically "Aberrant Dragonmark Magneto". We agree that in our campaign this was the secret of the War of the Marked... a previous generation of Aberrant marked had learned how to use their marks to power psionics, meaning that they were able to field an entire army of Mystics and pose a realistic threat to the regular Dragonmark Houses.
https://media.wizards.com/2017/dnd/downloads/UAMystic3.pdf
While 1 to 11th is technically only "half the levels", it covers the half that the vast majority of campaigns actually run in, so I think I gave the class a pretty good test run. I selected the Order of the Awakened as my subclass. By the time I retired the character at 11th level he had the following Talents/Disciplines
Talents
Mind Thrust
Mystic Hand
Mind Slam (Not sure I ever actually used this one as I didn't take it until level 10.)
Disciplines
Aura Sight
Mastery of Ice
Mastery of Water
Nomadic Step
Psionic Restoration
Psychic Assualt
Telepathic Contact
Note that I used the ability to switch out a Discipline upon level up liberally in early levels, so at various points in the campaign I tried out Mastery of Force and Psychic Disruption.
Overall, my DM declared that the Mystic was "Tier A, but not quite overpowered." I think I'd agree with that assessement.
One of the most powerful abilities the Mystic has is the ability to target Intelligence saves. Mind Thrust was my bread and butter early on, Psychic Assault came into its own with Ego Whip (a single target shutdown) and later Psychic Crush, and then the Telepathic Contact Discipline with a chain of Int-save based Paralyze or Dominate effects. Intelligence saves rather than Wisdom saves are so important because non-sapient monsters are going to be rolling with a -3 to their Int save, and there are a lot of big powerful, but non-sapient monsters in the DMG. Granted that might change from levels 11+ as non-intelligent monsters get thinner on the ground, but see my remark about where most campaigns spent their time.
The other ability I really have to single out is the Nomadic Step Discipline from Level 7 onwards.
- Phantom Caravan (6pp): You + 6 willing creatures within 60 feet can teleport to a place you can see within one mile. (Or to a place you can't see within one mile if you dropped a Nomadic Anchor (1pp) power there within the past 8 hours.)
- Nomad's Gate (7pp): Open a Gate between your current location and a location within one mile you've seen within the past 24 hours.
Yes, you never get the world-hopping ability of an Arcane caster's teleport circle, which is why the class is not quite overpowered, but Phantom Caravan is crazy. My character was able to grant the whole party enormous tactical flexibility and emergency escape whenever we needed it. We'd zip past obstacles, outpace enemies, and appear behind enemy lines. These are expensive powers, sure, so I couldn't just use them all the time, but there so many occasions when it came in handy:
- Exploring the tunnels underneath Sharn? Having left a Nomadic Anchor behind, I just blipped out out when we wanted to leave.
- White Dragon lair at the top of a nearly unscalable sheer cliff? I teleported us to the top. When we find the dragon, I bring the party fighter and paladin right up in its face rather that it being able to keep its distance.
- Ambushed by Displacer beasts while traveling outdoors on plain? I teleport us a half mile away.
- Assaulting a literal city of Fire Giants? I blip us straight to the foot of the tower where their king lives, we launch a lightning raid to steal precious artifacts, and then Nomad's Gate outside the city to flee.
Anyway, my understanding is that they're going to rewrite the whole Mystic pretty much from scratch, but it was definitely an interesting experience to play one. Careful power selection was able to cover for a lot of the class's weaknesses, but the power points led to a tendency to Nova that had to be carefully managed. The free Telepathy was all right too; even if the other PCs couldn't talk back I was able to give them information effectively on a number of locations.
Addendum: As far as Eberron-specific stuff, I took the "Aberrant Dragonmark" feat and eventually met up with the Aberrant refugee "House" in Sharn. Since my conceit was that my character's psionic abilities were being powered by his Aberrant mark, I started to train the other Aberrant Marked in how to use their own marks to power psionics and ended the campaign as basically "Aberrant Dragonmark Magneto". We agree that in our campaign this was the secret of the War of the Marked... a previous generation of Aberrant marked had learned how to use their marks to power psionics, meaning that they were able to field an entire army of Mystics and pose a realistic threat to the regular Dragonmark Houses.