Concluding this series of playtest notes with the Mystic. For those interested, I've also done similar threads listing notes from my playtests for Starfinder's classes (i.e. the Envoy, Operative, Solarian, Soldier, and Witchwarper), Barathu ancestry, and guns. I'll split my post into sections, spoiler them, and add a TL;DR just so it's all a bit easier to navigate.
Methods:
Here are the methods I've used for my playtest:
Most of my playtests took place at levels 1-5, as I ran them mostly using the official Starfinder playtest scenarios and field tests. I ran some playtests at higher levels using Pathfinder content, but treated those as secondary to the playtest scenarios.
I ran my Mystic with a variety of party compositions, mostly with just other Starfinder classes. I eventually started adding Pathfinder classes into the mix, and treated those playtests as secondary.
I ran my Mystic under different ancestries, as I was playtesting those too.
I ran the scenarios RAW for the most part, only adjudicating when something broke or was missing from the rules (or the class's core features). I then started playing with certain parameters, like enemy behavior and compositions or the Mystic's features, and treated those findings as secondary.
As per standard, I maxed out the Mystic's Wisdom, then Dexterity, then Constitution. Thanks to the Mystic's Wisdom key attribute, I experimented with Strength, Intelligence, and Charisma as my fourth score.
I experimented with a bunch of different weapons and tried to "cast gun" when it felt appropriate. The pre-errata seeker rifle was obviously good for consistent damage, whereas a combination of laser pistol and carbon shield gave me a bunch more options in combat.
TL;DR: I ran the Mystic many times mainly through the official playtest scenarios at their low level range, using a variety of ancestries and party compositions. As I put the class through the same encounters, I altered some parameters over time to see how they would affect its performance.
Core Class:
Splitting my feedback on the class's core chassis and its feats for readability:
Let's talk about Mystic Bond/Vitality Network, the Mystic's defining class feature. I absolutely love it. The unrestricted range to the bond itself is perfect for a game that takes place across vast reaches of space (it also meant I didn't have to check for ranges if I wanted to know an ally's position during exploration), and Transfer Vitality is the perfect action for a caster: not only did its single-action cost make it the perfect third action on many of my turns, fitting neatly alongside my spell casts, the amount of healing I could provide on tap meant that I could choose almost any kind of spell I'd like, including a very aggressively-oriented repertoire, without feeling like I was compromising on the utility casters are known for. This alone was enough to make the Mystic feel like a standout caster, and in my opinion is one of the best-designed and implemented mechanics in the entire Starfinder playtest.
On a similar note, the unrestricted range to mystic bond makes for some really wacky and unique plays that the class's features and feats capitalize well on, such as Group Chat enabling telepathic communication. Although my playtesting was focused almost entirely around mechanics rather than broader roleplay, I did get major Sense8 vibes from the mystic's bonded allies all being intimately aware of one another and able to communicate with each other across potentially vast distances, which I really enjoyed and found full of roleplaying potential.
I very much enjoyed the Mystic's connections overall, and in general found the class's features quite generous in giving them flexibility and more things to do, including 3 focus spells. I will say that although I like the addition of a 19th-level bonus feature, like with the Witchwarper, I find that to be more the kind of thing a feat would provide, as casters in 2e already get a large boost at 19th level with their legendary spell proficiency and 10th-rank slot, and the Mystic is no exception.
As a side note, I quite like how the Mystic is encouraged to rank up their connection's skill in various ways, such as it increasing their vitality network's HP recovery or factoring into feats and focus spells like akashic fount. I'm on the fence about whether this should mean having the skill auto-scale, given how the Mystic probably gets a bit too much already (but then a lot of focus spells would fall off without that auto-scaling, creating a skill increase tax), but the existence of that scaling itself felt good and made the standard magic skill on a spellcasting class feel less perfunctory.
Akashic was quite a fun connection to play, as potent healing made it quite distinct from other occult casters, plus there was a neat combo with akashic fount and the free RK on the subclass's harmony. The subclass falls short on feat support though, which I'll talk about further down, and akashic assistent in the few times I used it seriously overperformed when I used the spell to Aid a martial class's attack rolls essentially for free and for an entire encounter. Given the spell's wording, I think the devs forgot that Aid can be used on attack rolls and not just skill checks, and the spell would be totally fine if it just worked on skills.
Elemental, by contrast, I think had a few issues: part of it was that most of the class's abilities felt like the optimal use case was to just dump lots of power onto a martial class, as elemental weapon + harmony meant you could pre-buff a martial to deal tons of extra damage on a hit. The other was that the harmony effect as written encourages not using an epiphany spell with a duration, because being able to stack lots of different types of persistent damage is really strong in and of itself. I feel part of this could be resolved by having the Mystic attune to one specific element at a time through daily preparations and a ten-minute activity that defines the element and damage type of various spells. Another part of addressing this could be to make elemental weapon's bonus damage specifically apply when wielded by the Mystic and not a bonded ally, or even just eliminate the bonus damage, as being able to create a weapon on the fly and choose what damage type it deals is already quite strong.
Healing was my favorite connection to use, and might very well be one of my favorite healers to play in all of 2e. The spell list and focus spells gave me basically everything I needed to be a great healer right off the bat, allowing me to pick any divine spells I wanted regardless of their healing capabilities, and the harmony effect made healing allies even more liberating, as I could heal essentially whenever I liked without feeling like I was wasting any Hit Points (and this in fact gave me momentum as I could easily refill my vitality network with overhealing for later use). Bonus points for the connection skill being Medicine, meaning I could spec into healing via skills and boost my Mystic powers even more, with Battle Medicine synergizing with my vitality network through harmony. Kudos to the Starfriends for designing a subclass that, in my experience, flowed beautifully and felt amazing to play. If I had to make one (very minor) criticism, it's that the mention of promession in the vital rebirth epiphany is redundant, as the spell is a death effect.
Rhythm felt quite decent to use, though the primal theming felt a bit off given how strongly tied music in 2e is to the soul, i.e. divine and occult magic, rather than anything to do with primal magic. The harmony effect I feel could also use some slightly different writing (the effect should just Sustain your epiphanies, as that's the thing you do to extend their duration by 1 round), and it also felt more restrictive than most other harmonies given its limitation to epiphany spells. I feel the harmony could have easily been extended to let you just Sustain anything by default, and then contribute one action towards casting an epiphany spell otherwise (as opposed to literally any 1-action focus spell as is currently the case).
Shadow was generally quite a decent subclass. The harmony effect worked well with both the Mystic thanks to their Stealth connection skill and a Sniper Operative, and less well on less stealthy party members. Shadow snap is a very strong spell, but also in my opinion poorly-worded right now: the stalk command implicitly expects its attack roll to deal the attack command's damage on a hit (and double damage on a critical hit), yet that is not a property implicit to attack rolls in 2e, so RAW the stalk command lets you make a spell attack roll that does nothing on a hit, and does nothing on a crit either if the triggering action was a ranged attack without the manipulate trait. The focus spell ought to be updated to describe how the shadow makes the same attack for both commands, and I also think the stalk command should have you use your reaction to make the attack, as otherwise it's just the attack command with the added prospect of potentially disrupting an important action (that, or the entire focus spell should just have the shadow stalk the target, and even then that should probably warrant a reaction cost).
My main criticism of the Mystic as a class is with its base stats: 4 slots per rank, 8 HP per level, and light armor proficiency is way too strong a combination by itself, in my opinion, let alone on a class that gets so much via their unique class features, subclass, and strong key attribute. The class needs to be pared down somewhere. I experimented with reducing the class's defenses, their spell slots per rank, and both, and in my experience the class felt the most balanced and functional with reduced defenses and no reduction to their spell slots per rank. Having more spells to choose from felt like an important part of the class's general freedom of choice, whereas their vitality network helped act as a buffer to their increased vulnerability when I reduced their HP and AC. I also experimented with changes to other classes during the latter parts of my playtest, and found that making the Mystic (and the Witchwarper) into a more fragile cloth caster worked fine when the Solarian and Soldier were changed to be better at attracting more enemy attention towards themselves. This makes me suspect that the Mystic's assumed need to have higher defenses in order to survive Starfinder's ranged meta stems more from shortcomings in the game's tank classes (which I discuss in my notes for those respective classes) than any problem with the ranged meta or the Mystic themselves.
On the flipside, the Mystic's Perception proficiency is stuck at trained at all levels, when every other class gets at least one proficiency increase as they level up. I'm glad the class got the weapon specialization feature they were missing added to them in the latest round of errata, but I feel the lack of expert Perception proficiency on the class is an oversight that still needs to be rectified.
Besides the above, the generally freeform nature of the Mystic's vitality network meant I got to "cast gun" as my third action quite easily. It felt good at levels 1-4, though distinctly less so once my weapon proficiency started falling off at higher levels, and after that I ended up relying more often on my vitality network. This still felt a lot more workable than with the Witchwarper, whose core mechanic felt like it needed much more action investment and wasn't nearly as functional.
When trying out fourth attributes, I found Intelligence to be a solid pick for the extra skills, especially on the Akashic connection for improved RK checks. Charisma also worked decently well when Demoralizing at close ranges, though I'm surprised to say Intelligence was the stronger performer overall. Strength did have some use when trying out a bone scepter build with Ebb & Flow, but otherwise I found it much less useful than the other two attributes, especially when feats like Cloud Storage further devalued the stat. Overall, the Mystic had a good choice of fourth score, which added to the class's overall feeling of freedom.
TL;DR: The Mystic's bond and vitality network worked incredibly well in my opinion, giving the class tremendous freedom of options and complementing their spellcasting perfectly. The class overall felt distinct from any other spellcaster in all the right ways, and their subclasses largely enhanced this with a clever choice of synergistic spells, harmony effects, and skills. The class felt overstatted, though, which I think could be solved by reducing their HP per level and defense proficiency to cloth caster levels, and they still need a proficiency bump to their Perception at later levels.
Feats:
I mostly focused on level 1-4 feats during my playtests, owing to the level range at which I mostly played:
In general, I really enjoyed choosing from and using the Mystic's feats. The integration of the class's vitality network, connections, and spell tradition into various feats made them feel much more bespoke than the feat selection I was generally used to with several casters in Pathfinder, and feats like Adaptive Defense and Ebb & Flow encouraged more aggressive playstyles using specific weapons.
The one major caveat to the above is that the Akashic connection and occult tradition felt generally less well-supported than the rest. The connection has no unique conversion feat at 12th level unlike the others, nor does occult have any bespoke 1st-level class feats. This isn't a huge oversight, but does make Akashic feel like an afterthought compared to the other connections, and could be remedied by just a few extra feats.
Cloud Storage was really fun to use simply for how silly it was and how convenient it made carrying items around. Being able to retrieve items from it out of any endpoint might perhaps trivialize traits like concealable, but otherwise this ended up feeling much more balanced than it read on paper.
Extended Vitality, by contrast, felt a touch more problematic simply because the extended range meant my Mystic could hang far, far back and still contribute heavily in encounters, without putting themselves at risk. The "same planet" restriction I feel also needs better wording, since several scenarios don't take place on a planet so much as a ship or space station: I ruled that the range extension still worked in those cases, but RAW the feat may very well do nothing in those circumstances, which would be a shame.
Curiously, there doesn't appear to be any feat that lets you refill your focus pool when you Refocus, even though that kind of feat is standard across other casters. Perhaps this was just for page space reasons, but otherwise I do think it would be worth including this for players who make especially heavy use of epiphany spells (which I did, especially with Rhythm letting me both Transfer Vitality and cast anthem on the same turn as when casting another spell).
TL;DR: I found the Mystic's feats did a terrific job of feeling both generally powerful and distinct to the class, addressing common concerns of caster feats in 2e. Besides certain unlimited-range feats needing a couple more checks to avoid abuse cases, my main recommendation would be to just give occult Mystics a bit more feat support to be in line with the others.
I saved the Mystic for last in posting my playtest notes here, as my experience of the class was the most positive, and I really had a blast playing one. They really felt distinct from any other caster I'd played, and in general came across as both a solid starter class and a good healer class for players who, for one reason or another, would not normally pick a healer in a tabletop game. You get to heal while blasting, laying down utility, or even just healing some more, and the class felt like they had some of the greatest freedom out of any caster, both in terms of actions and character build options. Aside from some issues with the character's base stats (they're overstatted and likely need less durability, but could also do with a proficiency bump to Perception at higher levels), and occult Mystics lacking feat support compared to the rest, there weren't very many real issues I took with the class. I've had some harsh words to say for some of the playtest's other classes, with several of them featuring design elements that gelled poorly with 2e's action economy or general design philosophy, but the Mystic by contrast I think was implemented in a way that made use of 2e's three-action economy and general approach to casters to the fullest. Kudos to the Starfriends for implementing the Mystic so well in 2e, I look forward to playing much more of the Mystic and even integrating them into my Pathfinder games.