Bulwark Arbite
 Arbites Build - Warhammer 40k: Darktide 

This build focuses on having high attack speed with massive stagger. The amount of both offensive and defensive buffs gained from staggering enemies allows you to take most stray hits with ease while hitting for absurdly high numbers. (Record test melee white hit 2600 on Crusher.)

The goal is to dig into melee and control enemies with stagger, while dealing out serious anti armor damage. The unlimited grenades allows you to buy time or gain some added crowd control, for when your active ability doesn't instantly reset.

Range weapon option is fairly subjective. I personally like having the MKVIII for both its versitility as a close ranged weapon and as a midrange fire support, but more importantly the 25% brittle alt round provides a lot of increased team damage for pesky targets. 

Melee I went with hammerblow (singe keeping up stagger really helps us) and oppurtunist just to help punch through armor, quickly dispatching maulers, crushers and armored ragers is the cornerstone of this build.

For range, I opted for two semi close options, which im not entierly sold on, but intended or not the added strength from full bore seems to be universal, and couples well with you dumping Forceful stacks.