Hold the line alongside your trusty dog. Aggresive frontline build with dog utility.
 Arbites Build - Warhammer 40k: Darktide 

Hello! Here is an arbites build that I have had great success with on auric and some upper mid havoc games. This is a build that dishes out lots of melee damage whilst still allowing you to take the hits and control the horde in typical arbites fashion. Add your trusty dog into the mix who will back you up for particularly messy situations and pick off those annoying ranged enemies; and there is quite little that the heretics can do to break you and get to your teammates. 

As always change the build to what you prefer and is fun for you!

General play-style
The front of the team is where you want to be for the most part. With your melee and ability you will naturally keep the horde under control, using Remote Detonationand/or your shotgun when the crowd gets extra packed or has many elites. Your dog and shotgun will be able to handle specialists pretty easily but of course be extra mindful for trappers. 

Your main weakness with this build (and for most arbitrators for that matter) is naturally going to be bosses/monstrosities. Just remember to play to your strengths and keep any incoming hordes in check as your team takes care of the boss, helping kill the boss if/when other enemies aren't much of an issue.

Melee

The Branx Mk VI Shock Maul and Suppression Shield is a weapon that compliments many arbites builds/play styles and here it is no different. Against crowds heavy-light spam works wonders; great cleave, stagger, and damage that is of course further enhanced by a lot of the talents we chose. If you want to quickly eliminate an elite like a crusher, a light attack into heavy-light or spamming light attacks will usually do the trick. Don't forget to also use your weapon special as not only is it great for quickly halting most human sized enemies like ragers, but it will also stop trappers as well!

Ranged

The Exaction Mk III Exterminator Shotgun is just a very versatile gun that is useful for killing specialists, elites, and general crowd clearing. The Exaction Mk VIII Exterminator Shotgun is also a very good choice and don't make me stop you from using it, but I find with this build I prefer having the wider shot spread over the more centralised single target shot. Also worth mentioning the mark 3 has a larger ammo pool that combined with the talent Ammo Belt means you don't have to hesitate to use this gun usually if you are concerned about ammo. This is a primarily melee focused build but I often find myself using the shotgun quite often as you will have the ammo for it.

The Dog

Overall great support that compliments your ability to stay at the front dealing with the horde. Razor-Jaw Augment is probably the talent you are free to change the most if you want to use that talent somewhere else (especially since I am using Go Get 'Em!), but I find that your dog will often help with hordes as well so putting bleed on surrounding enemies is always welcome in my opinion. With how little your cooldown on Break the Line is too, Kill Order is bound to give you some value. Remember that Remote Detonation is also able to stagger monstrosities, so it is great for clutch revives!


Mandated edict: have fun!