Toxic Scum
 Hive Scum Build - Warhammer 40k: Darktide 

This is the main setup I've been running while helping people get up to Havoc 40 with some changes based on team comp/mission/modifiers. It gives me a good amount of support to people that don't have the best fundamentals as well as a being a huge safety net vs pox gas/corruption.

Build Design & Reasoning

The gimmick for this talent and stimm lab setup is to abuse the raw damage of Scum's toxin as much as possible while also being an excellent support for blight and pox gas. By having only 1 point in stimm lab (which one honestly doesn't matter) you have a 15 second Stimm Supply thanks to Practiced Deployment that is reduced on any kills with Sample Collector. Learning how to time the use of stimm supply for maximum Booby Trap effectiveness is essential for your damage. Outside of the boosts to crit chance, our only damage boosts come from Toxin Mania, Punching Above One's Weight, and Hive City Brawler, all of which are situational. Using Blackout with Pocket Toxin is great for CC to get out of tight spots while also being a good tool to farm stimm supply off lesser mobs quickly. That combo allows another character to bring a high-impact grenade such as Big Boom or Frag Bomb and horde the map grenades for key moments.

Stimm Labb

While you can regen your stim quickly in Havoc 30+ pretty much constantly even when using all 30 points, having access to a +7 toxin nuke every 15 seconds guaranteed (often much faster) that makes my team immune to corruption and heals what corruption they do have? I'll take that trade. 

Weapon Alternatives

Honestly, I've ran this build with most weapons and it will absolutely work with anything. Stimm Supply and the toxin stacking the class does will carry you through pretty much any problem so long as your fundamentals are strong. Take anything, you'll still kick ass.

Talent Alternatives

The only talents I would call vitally important to this build is Sample Collector, Practiced Deployment, Fast Acting Stimms, and the king: Booby Trap . I used to take Chem Grenade, but have recently fallen in love with the Blackout + Pocket Toxin combo. It allows another class to get more grenade drops since you can regen these while also providing strong CC for packs of Rotten Armour and applying 3 stacks of toxin. If you want a faster answer to Rotten Armour, switching to Big Boom and swapping Pocket Toxin with Extra Pouches is a solid choice. Also a good move if the rest of your team has nade regen/doesn't use them. 

You can keep the build intact and still get Pickpocket if you don't have a vet or just really like using the needle pistol. Just get rid of the damage reduction talents, they don't do much tbh. Like I said at the top, this build is to get pubs to H40 so I mainly grab Targeted Toxin for my teammates' sake. Just take off that, Hive City Brawler, and Regained Posture (or Chem Fortified, I just like the toughness regen) to get Critical Chance Boost, Ammo Jack , and Pickpocket.