During the Beta I have spent a somewhat unhealthy amount of hours playing my Psyker in the available content, chasing Penances with the help of my friends, farming upgrades and just playing the game for fun.
After all this time I still struggle to pinpoint what exactly a Psyker’s role is supposed to be in a Party at higher (4-5) difficulty levels.
My observation is that Psykers greatly suffer from hyperspecialisation depending on their Feat or Weapon choices which impairs them in either mixed engagements or in situations where their currently specced trump card isn’t required.
A Surge Staff Psyker brings excellent CC, stunning and staggering several Elites at a time, stunning and staggering Poxbursters and similar ambush enemies. However this loadout lacks in damage, it’s wave clearing ability is lackluster and apart from Brain Burst your only ranged option is the lackluster M1. Your damage against Bosses will also be rather on the low side.
A Voidstrike Staff Psyker brings almost unrivaled wave clearing ability, can engage Elites and Specialists at range, and at full charge the fireball slightly staggers even heavier or armored enemies. It is in my opinion the closest a Psyker gets to an all-rounder, however it trades away all the CC and limits your Boss damage to Brain Burst only - this Staff is completely useless against Bosses.
A Purgatus Staff Psyker brings wave and Specialist control, can Suppress most enemies the game throws at you and does substantial damage to everything in the Area of Effect of the Staff’s M2. In this case you trade away ALL your non-Brain Burst long range ability - not even M1 engages at range. This Staff however removes Bosses extremely well and can greatly help with multiple Carapace Armored enemy spawns.
An Accetar Recon Lasgun Psyker relies on the Kinetic Flayer Feat, with the weapon’s extreme rate of fire and great accuracy ensuring it procs exactly on cooldown. This way the Psyker avoids most of the Class’ core Perils mechanic, delivers substantial damage to most enemies (especially using a Lasgun with crit perks and the Infernus Blessing) and can swap to Brain Burst without worrying about Perils due to not using this mechanic in most engagements at all. The tradeoff is moderate wave clearing ability and lack of any utility, thus turning the Psyker into a worse Sharpshooter with Brain Burst.
This level of specialisation hurts Psykers in higher difficulty games, as they are often unable to respond to threats not even in an optimal way but at all. In comparison most other Classes can bring robust all-rounder weapons which ensure they’re almost never out of options.
Which brings me back to my main question: What is the Psyker’s role in a Party? Is it Elite/Specialist killing? Boss slaying? Or is it just CC support? Why does the Psyker have to forego all other aspects of his Class to specialise in only one?
It feels like the Psyker lacks a clear niche and just isn’t well rounded enough to find himself useful in at least most situations.