The issue of Psychic Immunity is currently a big deal for the Psylok. Psychic Immunity is simply a LOT more relevant in the current meta than other types of immunities. It is both common and protects against a lot of spells, conditions, and attacks. The next closest would be Poison Immunity, but I can't think of any creatures that deal poison damage with their attack. Some have effects that deal it though and there are several spells and conditions affected by it. Besides those two though, immunities don't generally have a huge impact.
Eventually though, I expect Acid, Flame, Hydro, Light, Lightning, and Wind immunity to be just as common and powerful as Psychic Immunity which will in turn make all of them have a smaller impact on the game in general.
Psylok will still have problems with it's attack being a Full Action though. The attack itself is very powerful, being able to slice through defenses, armor, and resillient like a hot knife through butter. It's just hard to pull off with a small flying pest that can't both move and attack in the same round. The Mind School has lots of spells and abilities to put and keep things in position though, so this could be compensated for.
However, it will still be a level 2 creature. Which in my experience, level 2 creatures are usually only popular with swarms or mages who have a "Pet" type ability. The Forcemaster lacks any "Pet" ability, so unless a Swarm becomes viable for her, I don't see any level 2 creatures being extremely popular.
All told, it is indeed a hard fix but I don't believe it is impossible. To illustrate my point, consider the following. If it was an Animal creature in the Nature School with the exact same stats except it dealt Lightning damage, I think Beastmasters would love it. They could get out a swarm fairly easily, use tanglevines/stranglevines to root enemies in place, and then fly in to chew through their worthless defenses. Add a Marked for Death to increase the damage by 50%. This comparison shows that it's the current state of the card pool that limits Psylok and not the creature itself that is "dead weight."