Trauma support (Brain Burst, Venting Shriek, Empowered Psionics)
 Psyker Build - Warhammer 40k: Darktide 

This is the build I've made for myself when using trauma staff, after lamenting about the state of the trauma staff.

I've come to enjoy the build a lot, so maybe others will enjoy it too.

Ended up doing this, as I'm not a fan of the other builds that use trauma staff on this site.

The idea of this build is to be an aggressive crowd controller, who can handle crusher trains and take care of specialists easily. You'll never be the #1 damage dealer with the trauma staff, but you can elevate the others, and protect them.

I'm still not sure if I'm completely happy with the build, as I'm questioning the validity of talents like Perilous Combustion and not having Kinetic Deflection. But overall I've been having a great time, especially on Auric Damnation.

It should be mentioned that I do a lot of slide dodging and similar things, and this build most likely isn't for everyone - nor would I consider it a "peak" build. It's just the build I've managed to make that makes me actually enjoy using the trauma staff.

Hope you enjoy it too. 

Just remember that stairs are our biggest enemy with the trauma staff, so be mindful of your aoe actually hitting anything when near them.

Gear

Curios

I've been using 2x toughness and 1x stamina. This is what I feel has worked the best for me, but do whatever feels better for you. Psykers generally have a pitiful amount of toughness, and the extra stamina helps for mobility and dealing with hordes. For perks having more health is nice, at least 1 gunner damage resistance helps (more than 1 has diminishing returns, but might be worth taking anyway), and cooldown reduction. I just picked what seemed most sensible, as these don't exactly match what I have exactly in-game with my imperfect items.

Melee

I've been using the Mk IV Duelling Sword as it is ridiculously good, has good mobility and all that jazz, but if you find a melee that works better for you, go nuts. I've been trying to find some others that might work better, but for now it's been working great as is.

Not sure how much value I'm getting from the blessing Precognition, but Uncanny Strike is doing some good work. For perks I've been sticking with Maniac (with crit you'll 1-tap mutants) and Carapace - though Flak might be better for the latter. I'm locked out of it anyway, and don't care enough to reroll.

Ranged

For the Trauma staff, I consider the Warp Flurry & Rending Shockwave to be the only viable blessings on the trauma staff - and it desperately needs a better selection.

- Terrifying Barrage is pointless, as this is a weapon that will stagger enemies.

- Focused Channelling is not good enough to justify losing the others blessings, and if you're getting hit you're already doing something wrong, get the melee out or get dodging.

- Warp Nexus, Blazing Spirit, Surge and Transfer Peril are all bad choices because this isn't a weapon that is good at achieving critical hits nor is it any good at hitting weak points - remember your aoe is mostly on the ground and weak points are typically at the top of enemies.

- Sustained Fire and Run 'n' Gun are just ... why even exist on this weapon.

+ Warp Flurry is a "must" because the trauma staff is slow at charging up, and when it gets intense you need that extra speed. It also really helps with quickly generating peril for more damage & toughness.

+ Rending Shockwave is what makes this weapon worth picking up in the first place, as you'll be tenderizing the enemies and make them easier to kill while also staggering them most of the time

Blitz

Why Brain Burst? I don't like Smite as it makes the game boring for everyone, and Assail feels superfluous as we can already handle hordes just fine and it's not good at targeting & killing specific enemies that are far away.

With Brain Burst and both its supporting talents, we have increased our damage output when using the sword or staff, when things get spicy we can Vent and quickly handle any nasty elite/specialists with high speed as the BB will charge really fast & generate less peril - you can also use it against monstrosities for extra damage output.

Aura

Make sure to get Psykinetic's Aura as it'll be quite good for cooldown reduction, and we'll also just go with Seer's Presence for more passive cooldown reduction. That'll have a better impact on everyone than extra damage on only elites or a measly 5% crit chance for everyone. Ogryns for example have barely any crit chance, so at best they'll have like 7% crit chance with that aura - and remember this isn't a build that relies much on critical hits.

Which is why I've skipped Empathetic Evasion, as we don't have a reliable way to keep crits going.

Ability

Venting  Shriek fits BB & Trauma staff perfectly, as you'll be dancing with the perils of the warp constantly, and I've gone with Creeping Flames because it generally feels better.

Make sure to grab Solidity for the delicious quell speed, as mentioned we'll be generating a lot.

Keystone

I was really torn on this, but after some experimenting, I decided to go with Empowered Psionics.

With EP we have some strong BB potential for when some nasty enemies are far away, and you just need a brief moment to handle them, as EP will buff your brainburst by making it a freebie, 50% faster and 50% more damage. Additionally when we use these buffed up BB, you'll be giving everyone around you toughness back, which helps increase their survivability. I've seen it really help someone out of a tough spot, and it feels quite good.

Why not Warp Siphon?

This keystone would definitely have increased our damage output, but every time you use Venting Shriek, you lose all your stacks and it's a "selfish" keystone, and I wanted this build to lean more towards support as the others damage output will generally be stronger than yours. I also want to be able to use Venting Shriek as much as I want, without worrying about losing precious warp stacks. Plus the insanely fast brain bursts that you get, can be quite clutch when it gets spicy.