HERE 'S JOHNNY (read desc)
 Hive Scum Build - Warhammer 40k: Darktide 

IMPORTANT!!! Use the Rashad Mk III Combat Axe !!! I simply couldn't pick the blessings on it because the website told me they are not available yet (lol) ,The Rashad Mk III Combat Axe has good cleave on LMB spam and a Precise heavy attack. You can swap out some things in this build because there is ALOT of playroom.

You can adjust the Contaminated Stimms to your preference but keep in mind that we want to have it's cooldown under 90 seconds for Chemical Dependency ,  the  way I've built it, you got some room and don't need to be on edge because of it`s CD, same goes for the CURIOS. I preffer a bigger HP Pool , if you think you're skilled enough you can go for 3x Stamina curios instead of Health/Toughness for even faster Attack speed due to (Swift Endurance) however I would recommend sticking to Toughness/HP for higher Havocs

You could switch out Coated Weaponry  at the bottom right tree for Channelled Aggression  in the Rampage! tree to burst Crusher even faster when you spam heavy attacks or swap the Aura for 5% bonus crit from (Anarchist)to  the 10% melee dmg one (Ruffian) and just replace carapace on the axe for the 5% missing crit. 

The reason we put stamina on axe is because of the bonus attack speed in the bottom left tree, We don't really need (A Tertium Welcome) because you will 1shot gunners most of the time anyways anything else doesn't really care for the 39-42 bonus dmg.

The mark of the needle pistol doesn't really matter , pick which 2nd mode of it you preffer i mostly use it to kill specials OR nuke bosses ( can use the rocket launcher for that aswell if you didn't change the blitz) you can use w/e ranged damage weapon you preffer aswell.

You can pick whichever Blitz you preffer , I'm simply taking the rocket launcher to nuke stuff I want gone asap when I need to clutch since it got a small buff today.

I played this build in a havoc 40 and it performed well enough to satisfy me.