Support Scum w/ Speed and Attack Boost
 Hive Scum Build - Warhammer 40k: Darktide 

Class Overview & TL;DR

Frontline speedy support scum. Deploy Stimm Supply crates loaded with massive speed and damage buffs while carving through hordes with your shivs. This build focuses on maximizing Stimm Supply uptime through Sample Collector and Practiced Deployment, allowing you to provide constant combat buffs to the entire team during hordes.
 

Gameplay Loop

Before you start playing Scum, any Scum build, remember ABD: Always Be Dodging.

The core goal of this build is to provide your team with near-permanent attack speed and damage boosting stimms. With this setup, every crate grants 20 seconds of:

• +50% reload speed
• -30% recoil
• +16% attack speed
• -50% stamina consumption
• +50% weapon swap speed
• +12% strength

The stamina reduction is particularly powerful and extremely underrated. For the duration of the buff it effectively doubles your available push attacks, doubles your sprint duration and doubles the amount of push attacks you can do which helps with creating space.

The interaction between Sample Collector and Practiced Deployment is what makes the build work. During hordes the cooldown of your 57 second stimm can often be reduced to 20-30~ seconds. As a result your teamwide buff will frequently be active more often than not during hordes.
 

Positioning & Melee Playstyle

Stay near the frontline alongside Zealots and melee-focused Ogryns. Your shivs synergize extremely well with Coated Weaponry and Splash Damage , as both sources of toxin damage contribute toward Sample Collector cooldown reduction.

Being positioned at the front also allows you to deploy crates directly onto teammates who are already fighting instantly boosting the effectiveness of the entire melee line who need your buffs the most.

Your primary source of toughness regeneration is Precision Violence which rewards aggressive melee combat. Keep fighting and slashing to keep your toughness up.
 

Survivability

Never forget ABD: Always Be Dodging.

The defensive core of this build is the combination of Nimble and Jittery . Together they allow your dodges to recover so quickly that you can stay mobile almost constantly during combat, with the added benefit of your dodges making you even faster than sprinting. The biggest pitfall for (newer) Hive Scum players is the lack of health and toughness compared to other classes, so rather than relying on toughness or damage reduction Hive Scum survives by avoiding damage altogether. Thankfully Hive Scum has some of the best ways of avoiding incoming damage altogether.

For when you do get hit in melee Precision Violence provides strong toughness recovery. Street Tough acts as a safety net against melee chip damage allowing you to shrug off a poxwalker every 8 seconds, while Tis but a Scratch helps mitigate ranged chip damage throughout the mission.
 

Offensive buffs for dodging

While Nimble and Jittery keep you alive, Float Like a Butterfly and your shiv blessings reward dodging by increading your damage. Constant dodging grants an additional 20% critical strike chance from your talents on top of an extra 20% crit chance on dodge from your shiv blessing and 45% finesse damage on your shivs.
 

Weapon Choices

Agripinaa Mk I Infantry Autogun 

The recommended ranged option.

The Agripinaa benefits heavily from your stimm buffs, especially reload speed and recoil reduction turning it into an accurate dealer of death for deleting specialists at range. The agri autogun's penetration also allows it to kill flamers and other priority targets through hordes.

Branx MkVI Needle Pistol 

Alternative option for players seeking additional boss damage.

Since the build spends most of its time in melee combat choose whichever ranged weapon best complements your personal playstyle.
 

Rationale

Why 12% Strength for 57 second base cooldown instead a 75 second maximum buff stimm?

After a few dozen hours of running this build i found that at most 12% strength version provides the best balance between buff effectiveness and cooldown frequency. While the larger strength bonus is attractive on paper and does still work well enough, the reduced cooldown achieved with the setup described in this guide results in significantly higher overall team buff uptime throughout a mission.

If you do want to buff-max then i suggest going down the +35% finesse +8% strength stimm path and making your melee shivs even deadlier, your zealots will love you for this too.
Ultimately i found 57 seconds to be the perfect cooldown for keeping up the teamwide stimm crate buff for most of a horde and minimizing downtime.

Why Reflex speed stimm (+50% reload speed, -30% recoil) instead of the +4% attack speed,slowdown immunity or the +10% move and dodgespeed stimm?

The main reason for this is my choice of ranged weapon, Agripinaa Mk I Infantry Autogun , benefits massively from the reload speed and recoil reduction, it allows your gun to be deadly precise. The other benefit of reload speed reduction for your team will be very appreciated by any ogryn Kickback users or general shotgun users in your party. 
The other two buffs on the speed tree i don't find worth the added 10 second cooldown for the buffs they provide, whereas the reload reduction can be used by almost all members of your team. While this build focuses mostly on melee and buffing your melee teammates, the ranged-heavy classes also benefit from your attack speed, weapon swap speed and strength buffs. Fun for everyone