Flamer/Hammer [fun and effective/ skill]
 Zealot Build - Warhammer 40k: Darktide 

Artemia Mk III Purgation Flamer [horde control/ mix hordes/ ok-ish boss damage ]

There is no horde anywhere in any difficulty, any modifier that could survive one mag of this weapon. 

remember to dodge-slide backward to avoid getting hit and when you run out of dodges or heretics are right in front of you use your ultimate (Fury of Faithfull) to stagger them while keeping your finger on the trigger. You can do this twice in a row (based on how many Fury charges you have).

Penetrating flames let us inflict a decent amount of damage on bosses. But, the only scenario where I recommend using the Flamer against bosses is when you are facing a beast of Nurgle surrounded by a horde. 

Tip for the Flamer:

• When you switch to your Flammer, throw a knife so you equip it faster. this is very beneficial when you are losing ground against a couple of elites such as Ragers and Maulers.
• A very fun and effective way to use the Flamer is to keep your hand on the trigger and dash forward using the ultimate. This will stagger them all right in front of you. just keep in mind to switch to your mele or use your ultimate a second time when they recover.

Crucis Mk II Thunder Hammer [single target/crowd control]

Combos: 

Horde Clear: Heavy attack + Heavy attack + push attack

•  Use a push attack when you are getting overwhelmed and need to refresh your dodges.
•  This combo is also the main way you will be triggering Invocation of Death Talent (200% ability cooldown on crit).  

Single Target [Bosses/ Elites except Gunners and shotgunners]: special activation + Heavy Attack.

• remember to hold your heavy for an extra second to charge of Thrust blessing on your weapon to inflict more damage.

Tips of the Hammer:

Movement is key for this weapon. facing regular hordes is not a big deal but when it comes to mixed hordes story changes.

I would recommend pulling out the Flamers and dealing with the mixed horde but with still need a tactic to be able to handle them with hammers as well.

Hold your block and dodge backward, keep your next target in mind, then charge your hammer and move forward and take care of it, now you are surrounded by the horde use your ultimate to stagger them all around you and then charge the weapon again and take care of another annoying enemy and then dodge back, repeat this until the mixed horde is a  turned into a regular horde and use then use Horde Clear combo. I would recommend killing the Crushers first since Fury does not stagger them. 

General Guide:

Remember you are using two heavy weapons with low mobility so to make this work you need to have mastered the basics of movement and also be comfortable with dodge-sliding to any direction. You are also using the throwing knife so if you can't consistently headshot gunners with knives then this build is not for you. if you do not have good movement then running two heavy weapons together means you will be spectating most of the game :D.