Relaxing Hive Scum
 Hive Scum Build - Warhammer 40k: Darktide 

Before I begin with discussing this build, I've left the last three points up to you to decide where they go; personally for me one has to go to Coated Weaponry  for one of them but the rest is up to you really.
This build is for casual, normal, and normal, semi-hardcore players; the Hive Scum is extremely bottom-heavy with survival perks unless you're extremely skilled, you'd instead take things "Float Like a Butterfly", "Slippery Customer", "Regained Posture", and "Like the Wind" but because trying to do the incredibly skilled player abilities of constantly using clipping, dodging, sliding AND OR slide dodging -  for me taking the ones I've chosen do far better for me in surviving.
No matter your skill level and ability, in my opinion, taking "Tis' But a Scratch", "Burst of Energy" and or "Hive City Brawler" is almost mandatory to not be a burden to your team.

The Tact Axe is my personal favorite for Hive Scum because of how well it works with HS's it's nodes and how you have an entire blessing dedicated to Critical Chance; and due to how your character swings the axe, it's very easy to get "Weak Spot" hits with.  In turn it helps you more easily bring your Stimm off cooldown when you take Sample Collector along with Coated Weaponry - with the right Stimm nodes you can go into Enhanced Desperado even faster.

For the Needler it's a personal preference, II's  alt-fire mode spreads toxin to a larger amount of enemies when the first enemy dies while VI has a harder hitting normal firing mode while it's alternate fire does small explosions which can hit enemies "Weakspot" box when they go off and pending on the height of enemies. 

The Play Loop
When against Hordes and using the Needler VI - Alt-Fire then pop Ability and just shoot everything in sight; if it's anything above chaff enemies switch to its normal mode and fire three needles into the target and watch them fall over dead (same for bosses, just a lot more shots)
Then, when your ability ends, switch to your melee, shoot yourself with your estrogen shot and start lobbin' heads and in a few kills your ability should be off cooldown to then go back in and repeat the process all over again.