BLENDER SCUM
 Hive Scum Build - Warhammer 40k: Darktide 

Kill Crusher with heavy melee attacks, preferably with 3+ shots of Branx MKII Needle Pistol if theres too many use Boom Bringer instead. You can use Rampage! but its not really needed if you're fighting less than 3 or so. But if theres a mixed horde you should use it anyway

Kill gunners by shooting from cover if you want to be safe. Its much riskier but you can also run at them with the pistol using Run 'n' Gun Stripped Down and sliding to avoid shots and shoot back. If they're close enough Rampage! can be enough to get you there.

Use the Branx MKII Needle Pistol for big poxwalker hordes,Rampage! for medium armored hordes Boom Bringer for the biggest hordes. Rampage! is great for restoring your toughness in a pinch or if you get surrounded. Prioritize dodging over blocking you need stamina for Swift Endurance 

Bosses you can unload with the Branx MKII Needle Pistol for bonus damage, then Rampage! and stimm. For Scab Captain and Rinda Karnak or Rodin Karnak use stimm and focus on light attacks while their shields are up, Rampage! after their shields are down for some great damage. 

 The Improvised Mk I Shivs special attack, the throwing knife, is also great for killing ragers, especially since they run straight at you so they're easy to hit. 

Branx MKII Needle Pistolalt fire mode is great for reducing your stimm cooldown, shoot a few times into a horde as you're running in then kill them normally

Testing results: 

Targeted Toxin is really hard to tell how good it is, if you're good at switching to Branx MKII Needle Pistol and using the blue setting alt fire to spread tox it probably helps a lot 

Barrage IV is a good buff on the stim, you dont have very much damage reduction and this gives you 16% and heals 25% toughness too. Regain tho its kinda slow, basically a worse version of Enemies Within, Enemies Without from zealot or Resurgence from Skitari. 10 second longer cooldown on the stim is a big downside, so if you're use to using your stim constantly then it might genuinely not be worth it. If you rarely use your stim then that downside doesnt matter. 

Lacerate vs Precognition im not sure but they're both better than Flesh Tearer If you get a crit youre already are really close to killing your target and you have Coated Weaponry to clean up anyway. Lacerate is better for clearing hordes Precognition i think is better for elites

Executor is probably the next best blessing for the shivs, especially if you're good at hitting weakspots on elites, cant really tell if its better than Precognition 

Toxin Mania has bad uptime in practice

Hyper-Violence really amazing psudeo-cleave for very fast attacking weapons, if you're fighting elites you can heavy attack into a random poxwalker then immediately strike an elite for bonus damage too.

Forge's Bellow is surprisingly good for when you get overwhelmed, the 2nd shout almost never does anything tho

Adrenaline Unbound toughness regen is really good on this class for when you're fighting in a massive horde