Red Zone Psyker, (Will it blend? Probably, it is a dream after all)
 Psyker Build - Warhammer 40k: Darktide 

This started as an attempted Heavy Sword build, leaning into Crits as you would expect. 
However after giving up and just embracing my Beloved's magic two handed food processor (Covenant Mk VI Blaze Force Greatsword is my preference for the simple move set) I found this build just flew. 

WHY? The Psykers talent tree has a few nice little nodes that empower you for having high peril. Peril is the unique resource for Psykers that careful management of allows you to build very powerful talent weapon combinations such as Azyr Psyker/Smite/Venting Shriek, or Rats trauma psyker. These typically reward a playstyle that actively builds and then dissipates peril.

Forget management! Turn your Peril to 11 and swing away. The core idea is you generate Peril, critical Peril powers your damage via "Warp Rider", your toughness damage reduction via "One with the Warp " and your weapon cleave via "Warp Splitting ". 

All Force swords and Psyker Staves allow you the blessing of "Unstable Power ", further utilising high Peril for a damage buff. Important to note that this build does not do well with staff weapons (at least for me) as its too easy to blew yourself up. 
Also "Unstable Power" isn't just a straight damage buff, it increases the strength of the weapon, so improves all aspects of it.
 

Peril? Always needs to be high to be effective. Fortunately there are many great nodes in the talent tree that allow you to build peril, all of the Blitz do this, as does Scrier's Gaze .

Scrier's Gaze is the go to Peril generator, it increase your damage, toughness damage reduction etc (take “Precognition ” if you have a weapon that benefits from Finesse damage boosts) , it is also one of the key toughness generators in a build that is light on ways to generate toughness, especially compared to other Psyker builds.

Toughness generation comes from “Warp Expenditure” and “Mettle”, Melee attacks and critical hits respectively.

Survivability, comes from stacking damage resistance from “Immaterial Focus ”, “One with the Warp ”, “Just a Dream ”, “Kinetic Deflection ” and “Warp Ghost ”. And " Disrupt Destiny”

“Just a Dream” coverts 25% of incoming damage to Peril while below Critical Peril.

“Kinetic Deflection ” converts spent stamina from blocking to Peril, whilst below Critical Peril.

You want this, High peril fuels  “One with the Warp ”. This is what helps keep you at High Peril.

What about blowing up from too high peril? and not using something like “Warp Unbound ”, or “Crystalline Will ” as a safety measure?
It should not be necessary. This build does not actively use Peril as ammo for a staff, or fuel for a Blitz. 

The Blitz are interchangeable entirely in this build, however there is a reason I have chosen to take “Smite ” with “Charged Strike ”. 
One of the nicest, in my opinion, Blitz combination for a melee Psyker build is “Brain Rupture ” and “Kinetic Flayer ” which is lovely to see go off in the middle of a mixed horde, handily indicating that there was something nasty hiding in the chaff. However, it doesn’t work at Critical Peril which is where this build should be, all the time. 
So “Charged Strike ” is a nice second option, the lingering DoT effect of the electrocute is also empowered by the Critical Peril (Warp Rider). A fully empowered overhead heavy attack with 30s Scrier's Gaze stack, and 25 stacks of Disrupt Destiny should kill pretty much anything, and the things stood behind it, baring a boss of course. If it doesn’t then the Electrocute should finish it off. Also repeated Heavy attacks into a boss keeps a constant trickle of additional, DoT, damage on them as well.

With “Psykinetic's Aura ” and Ability Cool Down reduction on at least two of your three curios, you should be able to reduce the cool down on Scriers Gaze significantly, with enough specialist kills Scriers Gaze will frequently be ready to go again when the one you are in drops. Do not be afraid to pop it again, it clears 50% of your peril, technically lowering your damage and defence buffs from being at Critical peril, but making up from that with the damage and defence boosts from being in Scriers Gaze.