Lonewolf Arbites (Current)
 Arbites Build - Warhammer 40k: Darktide 

This is my favorite variation of the Lone Wolf build. It's a great all-rounder that is able to dish out plenty of damage and survive in the highest difficulties.

Short Link: https://youtube.com/shorts/A0PRnjO02AA?feature=share

Pros: Fantastic damage and survivability against all targets and nearly any range.

Cons: Playing without the dog can be detrimental at times, as the dog offers a lot of forgiveness. Getting grabbed my Chaos Spawn and Mutants typically isn't a big deal and you're practically immune to Pox Hounds. Without the dog you need to play like any of the other classes.

Weapons

The best melee weapon for the Arbitrator is currently the Arbites Shock Maul with All or Nothing and Execution. The Push Attack / Heavy Attack combo has phenomenal Horde Clear and the Heavy attack Special Attack combo has amazing single target damage + electrocution application. 

For your ranged weapon I would recommend either variant of the Exterminator Shotgun, but I really like the Bolt Pistol because of how fast it is and because of its ability to quickly apply bleed with the Puncture blessing. I love running Puncture on this build because it's really easy to build up a 110% increase to your damage against Monstrosities, making 16 stacks of bleed VERY potent.

Curios

For Curios I run a balanced setup with 2 toughness and 1 stamina. Grab Ability Cooldown, Stamina Regeneration, Gunner Damage Resistance, Sprint Efficiency, and Block Efficiency. You're going to be using your ability whenever it's up so you really want as much cooldown reduction as you can get and stacking stamina benefits makes surviving much easier. Stacking toughness curios allows you to mitigate more damage in the long run.

Stamina is important with the Arbites Shock Maul because we SPAM the Push Attack Heavy attack combo, it's just that good.

Talents

Hammer of Judgement, Force of Will, Concussive, Up Close, and Walk It Off are phenomenal survivability talents that we can take because we're not running a pet. 

For our blitz we take the Arbites Grenade because it allows us to deal massive AoE damage really quickly and stagger bosses on demand.

Concussive is a must have on any Arbites build because it allows your attacks to treat any enemy as if it's Staggered. This triggers all sorts of defensive and offensive bonuses. Suppression Protocols is phenomenal for us because we have so much cleave and we will constantly be proccing this.

For our Aura we take Breaking Dissent, which will combo with Concussive because it makes enemies who we don't technically stagger count as being staggered. This gives our entire team a 10% damage increase on enemies that we are melee attacking.

Lone Wolf is a very interesting keystone for the Arbites but I wouldn't consider it to be exclusively better than having a pet - they're just different playstyles. The benefits of having an extra Blitz, getting an extra Blitz back every 60 seconds, having 10% increased damage and attack speed and 15% damage reduction provide some major bonuses that allow your combos to really smash enemies while surviving many things that other classes just currently can't in game right now.

With Lone Wolf I like to build really heavily into melee, taking passives such as Target the Weak and The Emperor's Fist to really take advantage of all of the attack speed, cleave, and speed this build has.

Additionally I've gotten used to taking Judicious Efficiency, Rapid Movement, and Street Smarts with all of my Arbitrator builds. These passives provide some massive quality of life and will save you a lot time or give you a lot of much needed leeway in the middle of combat.

Increase all Damage by % Talents: Breaking Dissent, Arbites Revelatum, Justified Measures, Weight of the Lex and Lone Wolf. 65% obtainable damage increase on ALL damage.

Monstrosity Hunter. 20% increased damage against Monstrosities.

Break the Line. 25% increased damage on all attacks. 

Total damage increase = 110% on ALL your attacks against Monstrosities.

Have fun!