Soulblaze/BB for pubs
 Psyker Build - Warhammer 40k: Darktide 

This is the build I run in damnation pubs. Really good allrounder, saves your own and your teammate's lives a lot, can run at all difficulty. Using Psykinetic's Wrath allows you to use 4 Brain Bursts(BB) on increased speed and reduced peril increase. Prioritize burning up the trash but if your and your ally's lives are threatened by a long ranged elite or a disabler (and you don't have someone in your team who snipes the elites fast, or your teammates trying to clear the trash always instead of focusing elites) CC the trash with Psykinetic's Wrath and do a fast BB on the high priority treath. This method also good for killing a group of ogryn type enemies, since BB opens bulwark's shield and goes behind it also will CC any kind of mobs.

DON'T use your soulblaze on bosses (Pleage Ogryn and Huge Snail Jabba thingy) it wont do shit dmg, either turbo bb them or go close and hit with your heavy special melee attack. But keep in mind, you will always help more if you kill the trash rather than damaging the boss. During Assassination target bosses focus on horde and not the boss, since you are the ultimate trash killer and CC king/queen, this makes your teammate's life much easier since they can focus fully on the boss.

For the staff, peril resistance and quell speed is really important to be at a high percantege, of course power is really important too and range aswell. This allows you to at least CC and if you have good power on your weapon kill the trashmobs too and use soulblaze for long time before you have to use your Quell ability. If the horde is not ended but you're almost at 100% peril just switch to melee for a bit.

Your melee weapon allows you to 1 hit stab trash shooter and melee scabs/drags on the face with the 1st hit of your light attack combo.

Of course take the perks with a grain of salt since rng is a fuck.

Mandatory perks:

staff and sword: Flak armour dmg on lvl 3 or 4

Curios: toughness regeneration on lvl 4.