PsyWhacker
 Psyker Build - Warhammer 40k: Darktide 

Become the unstoppable homicidal maniac you have always wanted to become.

Illisi Force Sword - even with the mobility nerfs (and significant damage boosts) this is going to be an incredible weapon. Once you are stacked, you can one shot crit, or one shot head shot Mutants with special. 
Perks: 

• Flak - Allows for one shot head shot specials vs Ragers, and easy body shots for most other elites.
• Mutant - Helps reach that mutant one shot, and also Ragers.

Blessings:

• Slaughterer - a single special can full stack this in a horde - still gives the most damage. Uncanny is fine as a replacement but not great.
• Shred - with everything going you will crit every other hit, making you a consistent death machine. BloodThirsty is fine, but makes you very reliant on spamming special to get your crits. 

Headhunter - Great weapons for boss damage and special killing, with amazing finesse. All Infantry Autoguns have great finesse and fit nicely here - and ones with a lot of consecutive crits like Columnus V can give insane toughness with Mettle and Gaze. Heavy Laspistol with Dumdum/Infernus is a great boss killer with little effort.

Perks: 

• Maniac - Almost all specials fall here, and is the primary purpose of the gun.
• Flak - Helps with killing ranged elites. Unyielding is very good here as well.

Blessings:

• Surgical - Or headhunter for the mk III due to consecutive crits.
• Opening Salvo - Helps hit numberous one shot body shots and headshots. Deadly Accurate is a good option if you hit heads enough.

Why Smite? Because we want Psykinetic's Aura, and Malefic Momentum, and it is the only way to get both. Don't bother using it. We need to use Gaze often, because we will intentionally let it burn out after 10-20 seconds due to the increasing peril costs. It doesn't go on CD when you use it, but rather when it ends so we are maxing CD reduction. 

Seer's Presence again we only take this out of necessity, though the CD doesn't hurt. Only way to get Scriers Gaze and One With The Warp. Gaze will keep up at very high peril, as can Illisi, making it easy to get max value. Combined with Endurance and the base nodes you will have 52%~ toughness damage reduction.

Disrupt Destiny is pretty difficult to use well with a primarily melee build but Doesn't reset on ult use, gives toughness regen and is just overall very strong. 


You can also run Warp Siphon:
Mettle, SoulStealer and Essence Harvest will give massive amounts of Toughness regen, even at range. Even after they nerf SoulStealer (as they should, it is busted) a single special on Illisi will easily kill 5-6 mobs giving you 62-75% of your entire toughness bar back even after the nerf. On a crit that is an extra 25-30%  or more depending on the number of enemies hit - meaning you can still insta fill your toughness bar post nerf with very little difficulty.

Inner Tranquility is pretty meh, Gaze instantly drains all our Warp charges, and our only other thing to use peril on is Illisi special, and we want that to generate peril when our ult is down.