I’ve leveled my Psyker to 30 and gave all four staves a shot.
I think the Voidstrike, Surge and Purgatus staves are decent. These all have their strong points and weaknesses. However the Trauma staff feels off, and I would suggest a change.
Currently in terms of roles, the Voidstrike staff is fantastic at thinning out hordes from afar, but struggles with flanking and up close enemies. The Surge staff is great at crowd control, but struggles with hordes. The Purgatus staff provides great close range damage, but leaves you with only brainburst to deal with enemies at range.
Then the Trauma staff. The area of effect explosion is clunky to use and it’s difficult to find situations where it shines.
My suggestion would be to attach a lingering ground field to its charge attack. Perhaps reduce the damage of the explosion, and have the ground field damage enemies that stay in it with soulfire, and have enemies that stand in the field take increased damage from melee attacks. That would open up a possible melee Psyker playstyle where the idea is to put a field down and then melee enemies that enter it. Compared to its current lackluster iteration it would be a unique playstyle that would also synergize well with the Preacher.