Melee DPS toughness sustain
 Hive Scum Build - Warhammer 40k: Darktide 

Relatively straight forward. Everyone goes crazy for chemical dependency, but I don't feel it's needed and I hate wasting a stimm just to keep the stacks up. People seem to be sleeping on Adrenaline Frenzy which is easy to keep up with dual shivs and focusing on crits.

Basic idea: Rush in with knives. Kill stuff. Use rampage when you need toughness back or DPS. Wait for rampage to be over. Stimm when you have enemies, especially a horde to kill, by the time the stimm is done, rampage will be back up. Rinse and repeat. For bosses you may want to do both at the same time. Adrenaline procs on hit so spam away and when adrenaline is active you get passive toughness regen of 5% a second which helps a lot, plus all the bonuses.

Use heavies on elites to have haymaker and Hyper-critical proc to eliminate them right away.

Some tips:

Use heavies with the shivs to move faster and slide just at the end of the attack to move closer to ranged enemies.
 

Your blinder blitz at auric with tox will kill all lesser enemies it hits, reducing the cool down on your stimm.
 

Use needle gun on beast of nurgle. Usually not worth getting in close, though you can at the beginning of rampage if you manage to get behind it to stun it with shout and land some good weakpoint hits in it's back. If it's aggroed on you though, just needle it.
 

If you use the blinder or alt fire on needle gun it will reduce cool down on stimm very quickly, as well as just light spamming into hordes.

If there's a lot of ranged fire and you can't slide/heavy chain your way there (not enough cover, too many enemies, etc.) Switch to needle gun and utilize the stripped down blessing to be immune to ranged damage.

Crit headshots with throwing knives and needle make the DoT stronger. Needle gun is useful on Ogyrn enemies when you have time and they're far away.

Use throwing knives on armored elites before getting to them for the talent bonuses.

Cheap shots procs off your grenades and shout from your rampage. Monsters are impacted by your shout and considered fully staggered.

Other options:

You can run toughness on the stim instead of cool down. Especially after rampage to negate the damage taken when it ends.
Run stamina regen instead of revive ally if you prefer, Hive scum has the highest inherent stamina regen so I don't feel I need it as much. 
You can remove some of the rampage modifiers if you want and add those points to other things if you want like toxic renewal if you want more defense.