Nukoto's Lead Storm Hive Scum
 Hive Scum Build - Warhammer 40k: Darktide 

When it comes to the Hive Scum, I've enjoyed playing around with ranged builds the most. Dancing around enemies while turning entire hordes in to swiss cheese with a barrage of bullets is undeniably fun, despite the class's shortcomings. This build aims to empower that fantasy as much as possible, while providing some much needed survivability and flexibility especially when your Ability and Stimm are on cooldown. 

The Basics:

For the purpose of riddling bodies full of holes, the Branx MkIII Dual Autopistols fit the bill perfectly. Speedload is a must to keep us shooting as much as possible. Blaze Away has been my other go to blessing pick but if you're struggling the ever reliable Inspiring Barrage can help keep your toughness topped off outside of Enhanced Desperado. Speaking of, Desperado is our best way to both stay alive and deal consistent damage, so we want to use it as much as possible. Taking Chemical Dependency as our Keystone means at max stacks we have a constant 30%+ Ability Cooldown Reduction. Focused Resolve will also restore a flat 5s upon exiting Desperado (you should pretty much always be able to activate this assuming you aren't focusing solely on a boss). Sample Collector helps replenish our Cartel Special Stimm faster, helping to feed in to the loop of maintaining Chemical Dependency stacks and therefore reducing the time spent outside of Desperado. Nothing lasts forever though, and when the Hive Scum is waiting for their Ability and Stimm to come back is when they are at their most vulnerable. Burst of Energy and Tis but a Scratch do a lot of heavy lifting to ensure you don't get punished too hard for taking a hit. Outside of that, take advantage of the increased dodging capabilities brought by Nimble and Jittery to stay out of harm's way. The rest of the talents are general improvements to ranged combat. Boosting things like damage, reload speed, ammo economy and critical strike chance. Having a decent chunk of crit also helps melee, and by taking the Chirurgeon's Mk IV Bone Saw we get the additional benefit of applying more Chem Toxin stacks when we crit. In less intense engagements it can be beneficial to get a few kills in with your Bone Saw since Chem Toxin infected kills will double the cooldown reduction on your Stimm granted by Sample Collector.

Stimm Lab:

I've opted to go for both Reflex  and Vultoprene II on the Stimm tree. Since ideally you want to be using your Stimm and Desperado together you actually wont get any benefit from taking Cooldown Regeneration buffs while Desperado is still active. We're already taking Chemical Dependency so picking  Chem Enhanced and Chem Fortified grant us even more benefits for Stimm use outside of the Lab tree. 

Considering Alternatives:

Maxed Out Chems sounds appealing at first glance but based on how Stimms currently work (cooldown only starts once duration of Stimm ends), a maxed out Lab Tree coupled with Long Lasting just takes too long to consistently stay at full stacks. This Keystone Modifier was clearly designed with using Stimm Supply in mind. There are a few ways to circumvent this. Reducing the potency of your Stimm and dropping Long Lasting can help maintain 4 stacks of Dependency. When playing with other Hive Scum, standing in their deployed Stimm Supply will increase your Dependency stacks. Personally, I feel like having a longer lasting, more potent Stimm is more beneficial over an extra 5% cooldown regen, crit and toughness damage reduction respectively. 

Blitz choice is more or less up to you. It doesn't have any bearing on the rest of the build and is largely player preference. As of 1.10.1 the Boom Bringer is in a pretty good spot and I've personally been enjoying using it more but both Blackout and Chem Grenade are respectable choices. The same extends somewhat to your choice for Melee. The Bonesaw lends itself naturally to both the class and our build but really if you enjoy another weapon more, use it! In which case swapping out a Talent for Coated Weaponry might help keep your Stimm cooldowns lower.
 

I'm by no means an expert and this is my first build here, but I hope this is enough information to get you in the game having fun on Hive Scum. I definitely agree with the sentiment that the class feels weak for just how much is demanded of the player but nevertheless I've still been enjoying it a ton. Thanks to anyone who takes the time to read this. Cheers!