The Arbinator with dog Havoc 40
 Arbites Build - Warhammer 40k: Darktide 

On launch this build made you literally unkillable but with enough damage to easily clutch on havoc 40 and carry it if not outright solo it and during a time Execution Order was not working properly so Forceful was the only reliable option.

Now you can use Execution Order with Malocator and Keeping Protocol by ditching Forceful and its extra nodes but its up to your personal preference of cleave/survivability vs. more dog and personal damage. Keeping Protocol combos well with Monstrosity Hunter, it allows you more autonomy killing them with any weapon and allows for veteran levels of damage while discharging a Locke Mk IIb Spearhead Boltgun .

You can use any of the arbites weapons either melee or ranged but both shotguns are goated. The Exaction Mk III Exterminator Shotgun  is better for crowd control with the special pellet using the wide duckbill spread and close up damage since it fires faster and has more damage if you can make all pellets hit while the Exaction Mk VIII Exterminator Shotgun is better for sniping specialists or bosses weak points.

Execution Order is a must for low visibility maps its like the veteran's Executioner's Stance allowing you to see specials and elites at distance and through walls but turned on all the time.

You can pick any aura you prefer but Breaking Dissent is more damage for your whole team and Part of the Squad is more survivality for the team and can combo with Benediction from a zealot for a great passive amount of toughness damage reduction. 

If you use any low carapace damage melee weapon then you can swap out something of your preference for Strike Down .

Castigator's Stance is the definition of meta it allows you to revive squad members while under fire, walk through flames, tank overheads and bursters at the same time when you need to hang on for dear life, throw hands and trade blows at the cost of only one node point.

You have a choice here to sacrifice some personal damage or survivability for more dog damage taking Razor-Jaw Augment and Serrated Maw but the bleed from Razor-Jaw Augment has been nerfed reworked a couple times, it's at it's weakest right now so it's really optional and niche to take it nowadays although with Execution Order it's a significant buff to how quickly your dog kills things you send after, including havoc Rotten Armour crushers, it's still indirectly nerfed when you also have the Contaminated Stimms and The Encroaching Garden modifiers offsetting the bite, bleed and eletrocute damage from your dog.