Love the smell of Ionized Flesh in the Mornin
 Psyker Build - Warhammer 40k: Darktide 

This is designed to maximize crit potential and basically spam Lightning unless you need to swap to melee. It's not the best for crowd clearing but you can survive in a crowd if you can manage your melee well. I've found that generally speaking Crit + Brain Rupture + 10% chance of a free brain rupture gets me just about anything except bosses killed in 1-3 hits. Worried about Peril? Just pop scrier's gaze and go nuts for awhile, you've got 11 seconds of completely free maximum peril damage bonus goodies. Anything that would die in 3 hits dies in 1-2 hits instead, 1 if you get the brain rupture proc. Basically impossible to stop as long as you've got a decent team around you handling some of the chaff and you're on top of your footwork/melee swapping. I used to run Smite instead of brain rupture but swapped to that to clear out some achievements, then I found that the brain rupture proc just works better and any time I would've used smite for CC I just swap to melee instead or dodge and zap. Duck and weave, duck and weave, zap zap slice slice. If you work up enough charge on your sword you just clear a whole wave anyways with the active ability including specials/elites, so what's the point of Smite? Plus I've found more often than not Smite is only great if you can be well defended while you're using it. Otherwise one good smack and you've gotta charge it again. While you're charging again you get smacked again. Better to just smack down a bunch of baddies with your huge cleave happy sword.

Technically you could swap to Prescience instead of Kinetic presence, I used to run that instead. It definitely will boost your crit potential a bit more, but with Scrier's gaze and the already great crit chance this has to begin with... I've started to find it's not really needed. Especially when brain rupture is basically it's own 10% crit with this anyhow. I maxed out around 1800-1900 crit damage, so with the extra 1350 crit you're very likely to smack down most anything that comes your way.

You can also just... charge your zap for full damage at any time. Warp Flurry makes it practically no time at all, by the time you get to a full charge you could probably have shot off 2 or 3 lesser zaps. With careful management of your charge and fingies, just zap everything to death. 

Peril? What Peril? The peril resistance in this build is nuts. It takes something like 20-40 zaps to build any kind of dangerous peril. As mentioned earlier, scrier's gaze is your safety net so if you really do just need to full auto the zappy zaps... just pop gaze and go for it. As long as you've been killing elites/specials your warp charges will bring it back up and ready to go in no time at all. If you want gaze to be more effective, just quell every few moments and let it build up charges. Especially when going after monstrosities managing Gaze is extremely useful. Once you've built up max gaze charges just let your peril hit max and enjoy 11 seconds of unparalleled super damage. There exists a mod that will put a counter on screen for this too to help you manage it better. Just quell a little bit before it ends or right as it ends and you're fine. 

I will say though I may be underestimating the value of finesse on the sword, I've been looking for a version that's got max finesse and min warp resistance since this build doesn't give a crap about peril, but what's on here is exactly what I use all day every day. 

Changes:
Swapped tranquility on the sword to Unstable Power, works out way better when choppin' through chaff.

Switched from Brain burst to Assail, at first it was just to get the penances for Assail but as I used it more and more I find it works extremely well for clearing small hordes of specialists and elites. Not super effective against large hordes, but it can definitely help thin their numbers if it looks like folks are getting overwhelmed. I've also found it's very helpful if you've got Ogryn buddies who need a little bit of cover from attacks from behind. Built the way it is now, there's a little less survivability here and there because of the loss of One with the Warp, but as long as you maintain damage output and keep dodging effectively you're fine. Don't need to dodge if your enemies are all dead! Prescience also just enhances the crit focus of this build.