Stand your Ground
 Psyker Build - Warhammer 40k: Darktide 

Pretty standard build that relies on the passive Toughness Regen from Essence Harvest and Dome while allowing for back-to-back domes through cooldown reduction.

I prefer the safety of Telekine Dome for the whole team over Scrier's but they are pretty much interchangeable with some rearranging.

Which FGS is better?

You can go with Mk6 for the easier stab but and you'll have a harder time quelling should you go with Scier's (By Crack of Bone). 

Mk8 FGS wide swings make it much more consistent to hit weak-points during hordes, and the Push Attack follow-up is the same Stab as the Mk6 H2, with a little extra oomph.

Both have an amazing push attack with great stagger and range, make use of it when things get sticky.

I prefer the Mk8, even when I run Dome.

Toughness Regen + Empyric Resolve = Bad?

While Empyric Resolve does reduce the Toughness Regen from the Dome and Essence Harvest, both combined still give us ~10% Toughness per second.

Coherency and Weapon Skills are unaffected, which is why Momentum will actually be our strongest tool to regenerate Toughness while surrounded.

I want Scrier's!

1. Replace Seer's with Prescience
2. Take Scrier's via Empathic Evasion, do not take One with the Warp
   1. Take Endurance and Reality Anchor
   2. Pick up Crack of Bone instead of Warp Splitting
   3. Optionally replace Deflector with Unstable Power, if you don't need the block efficiency. You are already counting as dodging most of the time, so ranged blocks are not needed.
3. Pick up Kinetic Deflect & Warp Rider on the way to the bottom section.
   1. No need for Surety of Arms with Scier's Gaze, but on dome we need it to keep Peril high
4. Warp Battery isn't needed, I suggest not picking up True Aim and the Movement speed node
   1. The extra points go into Mettle and Warp Expenditure

Why Double-Barrel?

Because I am so used to my DB deleting things on my Weapon Spec build, that I really wanted to keep it... That's it. It almost feels the same, with the reload speed from Both Barrels and Surety of Arms. Plus the guaranteed crit every 5 Weakspot kills letting you delete mixed hordes with Manstopper from the safety of your dome.

If you want to use a Force Staff instead, just unskill of Surety of Arms and put the point wherever you see fit.