Actual Chorus Meta (Havoc 40)
 Zealot Build - Warhammer 40k: Darktide 

No beef to the person that made that other build, but the issue is that there's 1 huge flaw which makes me go crazy every time I see this build in the Party Finder and makes me wanna instantly reject everyone who has it.

Munitorum Mk X Relic Blade SHOULD NOT BE PAIRED WITH Chorus of Spiritual Fortitude .

They are anti-synergy between each other. A good Chorus of Spiritual Fortitude build should always prioritize the highest uptime as possible, this way your team can be safer for more time, as well as you having the option to use book whenever you need to. A good Munitorum Mk X Relic Blade build should have considerable amount of Attack Speed bonuses. This can come from a combination of Fury of the Faithful, Inexorable Judgement and/or Martyrdom .

You're already seeing the issue aren't you? Munitorum Mk X Relic Blade+ Chorus of Spiritual Fortitude results in the Relic Blade not being able to reach its potential because you aren't getting attack speed bonuses, and it also results in book not having the best uptime it could ever have.
You end up with mid damage, mid book uptime, and the moment you're the one that needs to clutch (which Zealot SHOULD BE THE BEST AT), you simply can't.

So what melee should we choose for Book? There are 2 types of choices:
- Weapons that can handle themselves without point investment (Maccabian Mk IV Duelling Sword)
- Weapons that have crit bonuses (Catachan Mk VI Combat Blade and Atrox Mk VII Tactical Axe)

These will allow you to benefit from Blazing Piety , as well as have the best possible uptime for Book. As a nice bonus, these weapons are a lot better at clutch situations than a Munitorum Mk X Relic Blade with no attack speed bonuses could.

IMPORTANT NOTE! If you pick up either Catachan Mk VI Combat Blade or Atrox Mk VII Tactical Axe , then do the following changes:
- Remove Movement Speed Boost and Pious Cut-Throat 
- Add Infectious Zeal and Invocation of Death 

Other talents that could be changed:
- Feel free to switch Benedictionfor Zealous . Zealous is genuienly an extremely strong aura, even better than Benediction but most players don't know how to benefit from it. Use Beacon of Purity if the current modifier is Blight Spreads
- Feel free to switch Shield of Contempt for Against the Odds if you confident about your team not taking HP damage
- Feel free to switch Thy Wrath be Swift for Prime Target or Infectious Zeal (if you don't already have it) if you're confident in your positioning

Other melee weapon choices, as I mentioned before are also extremely viable, and after changing the talents to fit them correctly, build these melees the following way:
Catachan Mk VI Combat Blade Carapace + Unyielding, Uncanny Strike + Flesh Tearer, Mobility Dump Stat
Atrox Mk VII Tactical Axe Unarmored/Flak + Carapace, Headtaker + Brutal Momentum, Mobility Dump Stat

Have fun getting a lot more value in Havoc when running book!!! Oh one last thing, these weapons (and I guess build in general) rely a lot on being able to hit weakspots consistently for max damage, so start practicing those!