Max Crit VoidStrike
 Psyker Build - Warhammer 40k: Darktide 

UPDATE: sadly Souldrinker only has 50% uptime when you are the only Psyker, not worth the 2 points because the burn from Perilous Combustion is also only ~3% of your damage. I'm not gonna redo all the math for it. Also Warp Siphon does enough on its own, it's just there for a bit of cooldown, not worth spending more points in it.
Oh and since we have more points some may ask, why not Penetration of the Soul, it would actually be a ~20% damage increase, but only against Crusher, hardly needed nowadays.

MAX crit chance: 72.5% (with Souldrinker)

7.5% base crit chance

+10% staff

+20% Warp Nexus 

+15% talents (this was counting Souldrinker)

+20% Scrier's Gaze 

Without Warp Nexus: 52.5%

72.5÷52.5=1.38 => Warp Nexus increases crit rate by 38%

With Surge crits will deal MORE than double damage compared to a regular hit, so we can assume at least a 38% increase in DPS too, sometimes more. Compare that to Warp Flurry 25% faster casts, you may think that's a decent trade for convenience over DPS, after all in this case Warp Nexusis only 10% more DPS than what Warp Flurry provides. 

HOWEVER when Scrier's Gaze expires and you lose the +20% crit chance from it, now Warp Nexus is suddenly WAY better than Warp Flurry.
We can be certain that when Scrier's Gaze ends we will always be at 100% Peril for at least 10 seconds, thanks to Warp Unbound.

So instead of the max 72.5% we will have 52.5% crit chance, but a Warp Flurry build will only have 32.5% at most.

52.5÷32.5=1.61 => 61% increased crit rate from Warp Nexus when Scrier's Gaze is down.

In this case, that makes Warp Nexus a 29% higher increase in DPS compared to Warp Flurry.

And really it's not even that bad to have a slow cast speed on the Voidstrike staff, you just have to know to release it only after being at least 50% charged, around 60% is where you get most of your damage from my experience. Charging too much can also be an issue up close, because the projectile may pass through Maulers and Ragers when charged too much, so it will not stagger them with the explosion, and you'll get hit.

I think the Covenant Mk VIII Blaze Force Greatsword is much better than any of the single handed Force Swords, and more fun than the Dueling Sword anyway, so I'm glad there are just enough points to get the Lightning Speed and Anticipation nodes to make it easier to use in a pinch. You could take Warp Splitting instead of By Crack of Bone but more Cleave can be overkill sometimes, while the talent I picked lets you use your melee against hordes without Quelling to build up Scrier's Gaze.

Greatsword Heavy > Heavy, Strikedown loop is your best boss damage. Against Beast of Nurgle use Primary shots instead of charged shots or melee, unless it already ate someone, then you could actually save them with charged shots if they crit the weakspot.