Expedition Melee Scum
 Hive Scum Build - Warhammer 40k: Darktide 

This build has been working pretty well for me in Auric Expeditions. The stimm setup allows restoring 79% toughness every 42 seconds in addition to full toughness restore from Rampage!, which helps you stay topped off against ranged damage and/or when outside coherency. Maxed Out Chems is more useful than going for a full stimm lab branch due to the lower average enemy density in this mode. The knife has up to 95% crit chance when all buffs are active.

Needle pistol is pretty efficient at taking out all specialists/elites and DPSing bosses; it can kill most targets in 1 shot, reapers in 2 shots, and crushers in 3 shots. Against bosses, open by shooting them with 4 needles and then you'll be able to maintain max toxin stacks through Coated Weaponry. Spreading toxin from the Branx MKII Needle Pistoldoesn't feel important since enemies are usually spread out, so I recommended the Branx MkVI Needle Pistolfor extra toxin stacks on weakspot/crit hits. Pickpocket doesn't feel necessary because you can buy full ammo at the Sanctuary for 10 salvage.

There's probably a case for dropping Float Like a Butterfly to take Street Tough for more safety. Butterfly only has ~1/3 uptime in combat from my testing, which is good but not essential. I don't find myself getting surrounded very often in Expeditions, so I opted to skip Street Tough. Street Tough can save you from the occasional hound pounce though, which is valuable if you're away from teammates. Swapping out Coated Weaponry for Street Tough is also an option since CW is mostly relevant to crushers and bosses, which you can already shoot with the needle pistol for toxin DPS.