Double-Warp-Barrel
 Psyker Build - Warhammer 40k: Darktide 

Disclaimer: Not actually a gun psyker.

This one came to me in a dream from my beloved. 

It's basically (almost) your average Melee/Voidstrike psyker build with a slight twist. And that is, I realized that the True Aim talent that gives a free crit after five weakspot hits (which can be melee) functions not that differently from the Veteran's Weapon Specialist keystone, and could be used to trigger an automatic surge proc on your Voidstrike staff for a hit which can either almost kill a crusher when on low Disrupt Destiny/Scrier's Gaze stacks, or outright kill them if your stacks are high and you hit a headshot. Plus you shoot two warp balls of fury, so it works sort of kind of like a Double Barrel too. And Malefic Momentum helps with the idea.

I can't be really be bothered testing exactly the cutoff for breakpoints as there are many buffs that will influence your damage but it's good.

I have some other Voidstrike builds also if you're interested in trying alternative options. 

As usual, any Psyker without bubble is little squishy and less of an asset to the team's survivability but also like most Scrier's Gaze builds, you do a lot of damage to make up for it. 

This is pretty much a hybrid melee/ranged build that can swap between frontlining and providing decent ranged support against specialists and ranged enemies. 

Boss damage is mostly going to come from your sword but you can always free a teammate being digested with your staff.