PsyGivesTrauma
 Psyker Build - Warhammer 40k: Darktide 

Illisi (other force swords, or dueling swords... whatever tickles your fancy) Malefic Momentum was just a huge buff to this sword.
Perks:

• Flak - Most common you see in groups that you can't one shot with special.
• Maniac - helps two shot mutants if you don't have high peril, or many warp charges... not necessary but it is nice.

Blessings:

• Unstable - it is incredibly easy to keep high peril with Illisi so you can basically always get the buff even out of combat. Shred/Riposte are easy pickups if you don't want to play the peril game
• Slaughterer - this is a horde clearing weapon, and this blessing will help clear elites and specials in hordes. Uncanny, or Shred are very viable options here.
   

Trauma
Perks:

• Flak - with the increase to damage flak elites can now be one shot with this
• Unyielding - This now easily explodes most trash mobs and 1-2 shots many specials. Maniac is fine, but killing Ogryn and Bosses better is very nice.

Blessings:

• Rending - with the changes to Flak and carapace damage, and the buff to rending this is a great option now (also using shield to keep people from interrupting your charge) Focused channeling is a good alternative.
• Warp Flurry - not as strong as it once was, but you can keep stacks after quelling.
  note Full Charges will massively overkill trash mobs so you can cut your charges around half way to clear hordes.
   

Assail
Spam the ever loving heck out of this to kill ranged elites and specials - you will have so much peril resistance you can blow through all your charges without issues murdering anything beyond reach of Trauma staff. This is also the best way to build up peril for more damage on warp rider.

Telekine Shield
This, with Enervating Threshold will let you charge your Trauma staff with near impunity. Dome + Sancutary is better vs ranged mobs, but doesn't give you the stun for Mutants, Hounds and Bursters. Both are great options. 

Warp Siphon
This will provide you with ult cooldown, damage and peril resistance allowing you to spam Assail and your Staff till all heretics are a viscous goo on the Hab floor.
There are enough Elites, Specials, and mobs to get stacks from you don't have to worry about losing your stacks during hordes specially when you have Assail stacks ready.
Inner Tranquility + Empyric Resolve combines with Battle Meditation means you will essentially have infinite peril as long as you are killing any enemies with Trauma.

Essence Harvest is a great addition to toughness regen if you are struggling with that as the extra peril resist isn't necessary.