Psyker Bio-lightning Spam Build
 Psyker Build - Warhammer 40k: Darktide 

The goal of this build is to maximize damage against electrified targets while reducing peril build up as much as possible so that we can spam our staff secondary fire endlessly. Our main extreme range engagement tool is the staff primary fire with this build, which I find is sufficient for things like snipers or gunners at long range. This build doesn't use the bubble shield either, so you will have to be more mindful of moving from cover to cover or the gunners will make short work of your squishy psyker bod.  
The shock maul is the only weapon with any electricity boosts attributed to it so I went with it, but I imagine you could sub it out for just about any other melee weapon without really impacting the build as your main focus is the staff anyway. A chainsword or illisi force sword for extra crowd control are good alternatives.

We take most of the perks that reduce peril build up or quell peril on kill to allow us to blast away for as long as we can. We will gain stats as our peril builds up and always have venting shriek if we blow up, so we can blast away without fear as going high peril is a good thing with this build anyway.

Smite is chosen mainly for the electrified damage perk on Enfeeble but the active is still nice if you need a quick stunlock for a revive. I like to use a short blast of it to knock crowds over in melee too, but mostly just ignore it aside from the perk.

The soul blaze stuff is mainly to feed soul drinker, which is an excellent source of toughness regen while we manage hordes. We will be relying on this as our main way to regen toughness but should still use cover when we can. 

The dodge perks under the aura section make us immune to those annoying gunners for a short while every time we crit, which our secondary fire will be doing often. This buys us a little bit of time to react if caught out by gunners. We also run gunner damage reduction on the trinkets but can swap that out for other stuff if you feel comfortable fighting them without it. Stamina regen, ally revive speed, or sprint efficiency are good alternatives.

I have only ever played this build as high as Heresy so I cannot promise success if you take it to higher difficulties. Do so at your own discretion.