One would have thought all Psi powers sharing cooldowns, or Psi points, or something, would be a natural balancing choice. A Psi point system where they slowly regenerate Psi over time would be cool.
I would also say that if domination is going to be a thing it needs to be very very carefully balanced around.
Both of the final missions are difficult because of the length of the mission and the number of characters you have compared to the enemy; if you've played them you know what I mean. Psi Ops' domination ability let's you turn an andromedon to your side, which just completely fucks up the time economy of the game to the point of breaking it. So first of all, you turn a vast chunk of health over to your side AND you pretty much kill two enemies at the same time. Then until that andromedon dies you have 7 (or 8, or 12) units on your side, so now even if your psi soldier doesn't use any abilites for the rest of the game they're still going to be the most offensively powerful soldier, the toughest soldier, the fastest soldier, simply because getting a billion health and 4 actions a turn does that. I would actually say that even if psi ops ONLY got dominate and no other abilities, and it ONLY worked on andromedons which it doesn't, they would still be the best class. (side note: still think andromedons are an amazing enemy design)
In fact the ability to trade one turn for one turn even if the enemy is high health means that
stasis is arguably more useful than the other classes' last perks. The ability to save an ally from suicidal positioning, well, that's just gravy.
I think that we need some kind of lategame pressure or psi ops shouldn't be allowed to train every ability. The optimal way to play the game is to hold off on the final mission until you have 6 psi ops ideally with maxed out everything. Maybe if the gift were random, and you only got to level up a normal number of perks, you might only see dominate and psi lance once or twice even if you test your entire soldier pool. Of course that would mean the final encounter of the game would need to be toned down...
It sounds like the resistance psi faction will have to build up some kind of mana by fighting, maybe they want to add that system onto psi ops? It would be good. The narrative they're going for with psi ops seems to be godlike super-soldiers, going off of newcoms transhumanist themes. If we're going to go that way I think that psi ops should either be weak to psionic enemies, or they should be stronger against psionic enemies but weak against everything else. They should be constrained to a specific role on the team. Like how specialists are amazing but most of their shit is beneficial during the enemy turn, you can't expect specialists to do anything at all to a full health enemy during your turn and that means that even tho specialist is OP you don't want a 6 specialist team.