Purgatus and Deimos
 Psyker Build - Warhammer 40k: Darktide 

Deimos: with +flak armor damage you will kill mauler in one special attack. Deflector allow you to block bullets, slaughterer allow you to slay enemies as zealot, but thats not your work.

Purgatus: flak damage will be good, i have no idea what to place on second place, don't matter have i +25 to unarmored or not i dont have any unarmored alive around me. Warp flurry allow you to burn more then you load. Barrage do live of you teammates a bit safer, good when you burn ranged enemies.

Curious: +17+5+17+5+5 - with this i was playing for a long time, but somewhen i removed wound and placed stamina, cause all other things were useless and stamina at least allow me to run longer. Health? Are you going to take damage to health?! I have no idea what to place on last perk, try gunners/faster help for teamates/corruption rez.(or you will be half dead from one grim, you can get some shotsh from gunners/ranged enemies, but you are safe from all other things, if you can deal with them.) Block efficiency - the most important thing cause with that you can revive full team under attacks of demonheads/ogryns/new boss.(or maybe he will eat you) You can ignore 10 ragers around your teammate, but if you see one mauler you should kill him.(or push with f or sword.)

lvl5 - this allow you to ignore ranged enemies and gunners when you burn horde, also this thing protect you from random attacks, cause full shield safe your health from all damage at first attack.

lvl10 - resistance, this allow you to burn without rest when you have horde.

lvl15 - this thing reload you f faster and this is good help for teammates. Amasing with Ascending Blaze.

lvl 20 - peril shield, you dont need to move faster for a second of rest and you dont need to reduce damage from ranged enemies.(you will reg faster) This thing dont allow you to block maulers,crushers and boss with maul, but you can ignore all other enemies(except ranged, but you can press f) when someone downed.

lvl 25 - Wild fire allow you to do more damage. You don't need Kinetic Flayer cause you will burn. You don't need Warp battery cause this thing is not so usefull.(but good too) 

lvl 30 Ascending Blaze - this thing increase you damage, you see a horde, you press f at the same time with full charge of you stick, you don't see a horde but you are on full stacks again.

Don't forget that BB is safe from 95%peril, don't forget that you can edlessly push ragers when they are staing if you burn them with LMB.(good help for team)

You don't have anything except BB vs crushers and ranged enemies if they are too far,(but thats not a problem - just push crushers, and dodge to rangers to slay or burn them) you are worse than other psykers vs bosses, but damage is still ok, you don't have hordes and thats sad.