H40 relic blade stealth
 Zealot Build - Warhammer 40k: Darktide 

Use the sprint stab attack a lot, you can block cancel into a sprint to chain them together pretty fast. You can chunk bosses, make sure to get Sustained Assault and Disdain stacked before a sprint stab stealth into a bosses back. Ideally you would have Riposte and  Cranial Grounding stacked too, since cranial says weakspot dmg but its actually finesse dmg. 

Stealth makes reviving easy so you should try to pick up your allies asap. You can bring whatever grenade and whatever ranged weapon you prefer. I like a higher mobility ranged weapon to pair with the relic blade, but you could take a flamer or bolter if you want. 

Attack speed is overrated on the relic blade, martyrdom gives more than enough. The sprint stab is basically unaffected by attack speed and chaining them is the highest single target dps you can do. The mk2 horde clear combo also uses a heavy attack which is less affected by attack speed compared to lights (the period where you hold the attack button to heavy attack isn’t reduced by attack speed, just the swing animation).

3 wound curios because Holy Revenant will heal to exactly 2 wounds remaining when you have 7 wounds, thus giving you all 5 stacks of martyrdom. You could run a toughness or stamina curio if you prefer, but a health curio will actually be less hp at max stacks of martyrdom than an extra wound curio would be. I have found the most success with a wound curio.

On blight or tox gas maps, you could swap the minor +10% melee damage node for On the Brink. You could also swap it to Abolish Blasphemers if you prefer slightly more elite damage at the cost of boss and hordeclear dps. Abolish also works on ranged attacks so it might reach breakpoints into gunners with certain weapons, idk. It could also be put into Good Balance to have more damage resist.