Arbites
Up to 25-40% Strength, as Stamina depletes.
10-25% Rending vs Staggered Enemies.
14-20% Strength for 5s when every pellet in a shot hits the same enemy.
10-25% Damage vs Electrocuted enemies.
https://darktide.gameslantern.com/builds/9f3e12e1-f1d8-4c94-ac75-3675a20cb9f4/traded-my-dog-for-a-shock-mine
These changes are mainly to accommodate the Mastiff play style, you can also keep most of the original build, except for Lone Wolf.
The Shot Pistol & Riot Shield deals pretty insane damage to Bosses, under the condition that they are staggered/electrocuted:
High Voltage is only worth it if you specced into Voltaic Mandibles Augment. You can technically save that point since Remote Denotation also staggers bosses, but if you are out of charges, then miss out majorly on potential damage. The electrocution from the Mastiff pounce is a lot more consistent and does not rely on a cooldown.
The Riot Shield has the added benefit of being able to trigger Drive them Back's Cleave bonus. And it's very safe to take out hordes of gunners, since you can Block their shots while shooting back.