Guardian Zealot
 Zealot Build - Warhammer 40k: Darktide 

This build is meant to spam your chorus of spiritual fortitude and decrease the team's damage taken as much as possible. Stick near teammates and use your melee and chorus until you encounter a boss, then swap to your bolter and unload it as many times as it takes to deal a lot of damage, bleed, and debuff it with more damage taken from you and your allies. KEEP IN MIND the bolter is great at melting bosses, but has pretty bad accuracy and can't duel most ranged enemies other than snipers since they'll take multiple shots to bring down in higher ranks. Let your team take on ranged and you protect them from melee. The flame grenades are also very useful in situations where you're getting swarmed or there's a pack of pox hounds coming your way, just toss one on the ground, stand in the flames, and use chorus to stun the enemies in the flames while your team recovers. Blazing piety and scourge make it so you will get +45% crit rate while in large crowds fighting bosses or tanky enemies which will almost constantly give you the +200% recharge speed on chorus until everything around is dead. Also martyr's purpose gives you an emergency chorus if you take a crusher hammer to the face or get surprised by bursters. Those and the curios combine to give you a new chorus almost as fast as it takes to use it in the right situations of swarms and bosses (which means that this build will work better for you in higher difficulty missions) Holy cause added to chorus, shield of contempt, and until death also add great survivability to you and the team making the team tankier and lets you use the bonus recharge from martyr's purpose better in emergency situations.

TLDR: stay near teammates, spam chorus whenever possible, melee mostly and just use the bolter to melt bosses, flame grenades are good for holding off crowds on you. Build works best in high ranks / havoc where there's tons of enemies to stack blazing piety.