Always Insane!
 Psyker Build - Warhammer 40k: Darktide 

This build is an amazing all-rounder, but mainly extremely strong at killing ranged enemies. Its based all around crit chance, specificaly for “Surge”, making single target on LMB really strong and for “Empathic Evasion” which lets us stay near the frontline. It is also very dependant on perril, not only for damage, but also for defense. Perril is your friend, until you mess up. The gameplay is all about your perril going up and down, its not for everyone.

Its biggest weakness are bosses, thats why you can choose to have unyielding damage on maccabian sword. I prefer to roll carapace on it instead for ogryns and focus on all other mobs while other players are killing a boss, just my preferable strategy.

Perril - With more perril we get damage and crit chance for our staff. Always switch to staff when queling, it is important for this build to have as much quell speed as possible. 

Toughness - Our main source of toughness comes from quelling, combination of talents (Quietude + Mind in motion + Scrier’s Gaze + Solidity) gives us an amazing amount of toughness, while keeping decent mobility. Thats why you have to use scrier in the right times, preferably when you know, that you will need a lot of toughness recovery / single target damage. Spread enemies are also a threat, good time to use scrier for toughness. Preferably, you dont use scrier while facing a horde, trauma staff itself generates decent amount of perril, every kill gives us toughness and the rest we get from quelling, you dont want to fight peril at all cost, then its just inefficient.

Supporting others:

For ressing, I use 30% rev speed on curios. One full trauma charge on top of the downed person brings enough cc to any mob for us to safely ress, of course be aware if any bosses / muties / bursters / snipers / flamers / trappers / ranged elites are focusing you from afar.

Trauma charge can help anyone carrying batteries, its very usefull if you are at a safe spot to just spam trauma from a distance, or want to help somebody from getting cornered.

Bosses - as mentioned above, either focus all other mobs, or use melee heavy into weakspot for most efficient damage, while ranged, spaming LMB attack during scrier does mediocore damage to them.

Ogryns - you knock them down with Trauma charge, then finish them off with maccabian sword heavy attacks to weakspot as they fall, works like a charm.

Maulers - scrier + LMB spam kills them fairly quickly headshot or not. If its a group of maulers closing in quickly, same strategy as for ogryns works aswell.

Muties - 2 well aimed melee (heavy) attacks one as the mutie is aproaching into their head, second in the back of it as we dodge it, kills them quickly. For ranged kill LMB works fine.

Solo elites - LMB into weakspots does rly good damage with all the crit chance + surge perk, especialy when scrier is active.

Group of elites - the ideal timing for us is to have 20-30 stacks of scrier, then purposely letting it go to 100%, quelling with a staff to at least 20-30%, then spaming assail until the entire pack is dead. Obviously this timing isn’t always perfect, so using scrier on no stacks just before assail works just fine aswell. This works for - Ragers, shotgunners, gunners (including multiple reapers) armoured ragers. Anything up until flak armour dies very quickly. (Not maulers)

Specialist - LMB to their weakspots / bodies kills them quickly. For snipers if they are too far, RMB assail oneshots them with less aim required. 

Group of specialists - for muties only, its swordplay, for anything else - assail.

Burster - half charged trauma is a guranateed oneshot, LMB works fine for ranged, otherwise knockback…

Pack of dogs - assail is your best friend.

Ranged / melee non-elites - LMB.

Horde - Charging trauma to 50-100% depending on the amount of mobs youre trying to hit. If they are spread, idealy walk towards them, so they all stop near you / surround you, then finish them off. You can fairly easily survive any horde with no damage taken.

Summary:

Specialist / elite aoe - assail

Normal aoe - trauma charge

Muties + ogryns - sword heavy

Any single target - LMB

Bosses - focus surrounding enemies / sword / LMB

Until you get very comfortable with perril, I would suggest to use 1 wound in curios, so you can afford an error.

Enjoy