Book zealot for havoc 40 (Pubs)
 Zealot Build - Warhammer 40k: Darktide 

Meta in high rank havoc for each class

Best

• Book zealot (Chrous) + Flamer
• Bubble psyker + Purg flame staff (Warp Siphon)

Decent

• Taunt shield ogyrn + kickback (Could run pickaxe)
• Bubble Smiter (Empowered psionics)
• Bubble Void blast pysker (Aka Trauma staff)
• Shout weapon spec vet + Plasma

Check the link below for more details
https://www.reddit.com/r/DarkTide/comments/1ha7ja8/meta_builds_for_havoc_40_pubs_from_my_observation/

Intro 

For over 50+ games in havoc pubs, this guide is solely based on my experience in these pub games

This guide will mainly focus on book zealot, I might write bubble purg psyker or taunt ogryn another time

Your job as this build

• Get ult back as fast as possible, since it's the best CC and toughness regen tool in havoc games. (Yellow toughness is broken)
• Quickly take out specials or isolated gunners with knife or melee

Weapon 

• Dueling sword
  • Perk
    • Flak for most enemies in the game, unyielding for boss. U don't need carapace since pubs would press ult for it and u can build uncanny stacks
  • Blessing
    • Uncanny strike 
      • Armor penetration & rending would massively boost ur dot dmg (burn & bleed)
      • After reaching 15 burn stacks, u just start poking crushers head to boost dmg
        • Heavy + special (quick thrust with high stagger) to quickly build up uncanny stacks 
    • Shred
      • Mainly for invocating of death (CDR), since getting ur ult back is the most important
      • Heavy + special (quick thrust with high stagger) to quickly build up shred stacks 
      • Why not Riposte? 
        • It won't trigger when enemies get CCed, and high rank havoc is more about CC so u don't have good uptime with riposte
• Flamer
  • Take out huge pack of elites, it could also suppress ranged units
    • If ur teammates don't CC for u and ragers come close, try left click first for staggering 
  • Perk
    • Flak + elites 
  • Blessing
    • Blaze Away - boost dmg
    • Penetraing Flame - 20% rending debuff on everything u burn, good synergy with flame staff psyker
    • (X) Everlasting Flame - bad ammo economy (-75% ammo on highest havoc rank)

Curio

• At least two 17 toughness curio since -45 toughness on havoc 40 
• CDR & Stamina regen are just good 
• Gunner resist
  • Reduces any damage taken by Dreg Gunner, Scab Gunner, and Reaper (ranged and melee attacks)
  • Gunners get buffed in Grim Protocols patch + The Blight Spreads modifier on havoc (Shoot Faster, No toughness grace period)
    • Sometimes u  have to leave ur bubble to take out dispersed gunners in melee, gunner resist would help u negate some dmg
    • If u r confident with ur movement, u could swap this for toughness or sth else

Skill tree 

• Knife blitz 
  • Take out specials or isolate gunner
    • Even with Pus-Hardened Skin (Ranged dmg red = 10% + havoc rank), u can still two-tap them with headshots
    • Good ammo economy since u get them back by melee elites or specials
    • Most of high havoc pubs would struggle a bit with specials due to team comp
      • Purg smiter or fire nade zealot with flamer are not that efficient for taking out specials quickly
  • Immolation Grenade?
    • According to my experience on havoc pubs (Over 50+), most of zealots run with fire grenade
    • Since there are not that many grenades pickup in the first place, no point of running 2+ flame nade zealots in ur team comp
  • Other talent nodes 
    • The right branch has good synergy with crit build
      • Scourge - Melee critical hits apply Bleed (2 Stacks), Hits on bleeding enemies grant +10% CC for 3s. Stacks 3 times
      • Enduring faith - +50% Toughness Damage Reduction (TDR) on Critical Hit for 4s
    • Anoint in blood (Activate when ranged weapon is equipped)
      • Boost fire dmg
    • Second wind
      • Good toughness regen, and perform the best when fighting against ranged units
      • Extra toughness regen means u don't waste ult just on urself to get toughness back
• Combat ability - Chorus of Spiritual Fortitude
  • Best CC and toughness regen tool in the game. (Yep yellow toughness is broken)
  • Ult range increases with every pulse, and u can use it to suppress gunners group 
  • Forced stagger is only applied on the 1st, 3rd, 5th, and 7th pulse
    • Remember to  dodge specials during pulses, u don't want ur ult interrupted by a single mutant grab
  • Ecclesiarch's Call 
    • Channeling 5 pulses grants +20% Damage to you and Allies in Coherency. Lasts 10s
    • This node would massively boost all the dot dmg from flamer and purg staff
• Aura - Benediction
  • No beacon of purity? (Heal 1.5 Corruption from the current Wound for you and Allies in Coherency every 1s)
    • It's only from current would so plz don't step on it long enough to make corruption reach next wound
    • Most of zealots in high havoc rank run with purity aura for corruption dmg
    • In general, one purity aura is enough for The Blight Spreads modifier (Green poo)
      • As long as ur teammates don't intentionally bath in green poo, ur team should be good
      • If ur team somehow gets pinned into a narrow space with green poo everywhere, press book ult and ping them to walk out
• Other talent nodes
  • Until death & holy revenant
    • Shit happens, having one more chance is always good
  • Duelist
    • Good dmg boost for hordes and boss fight 
    • Also good for sliding out of the bubble to take out ranged units
• Keystone - Blazing Piety
  • Crit chance for proccing Invocation of Death (+200% Ability Cooldown Regeneration for 4s on Melee Critical Hits)
    • Zealot Base CC 5% + Shred blessing 20% + Blazing Piety 15% + Scourge 30% (Rather conditional)
      • 40-70% CC means u can reliably proc IoD & Enduring faith (50% TDR)
  • Stalwart (Triggering Fury Replenishes 50% Toughness  + 25% TDR during when active)
    • 25% TDR with high uptime is good
      • The requirement of Blazing Piety (25 Enemies have died within 25m) is very easy to meet
    • Stalwart would also replenishes extra 2% of max toughness per kill

Reference

• Zealot skill tree (By kuli)
  • https://steamcommunity.com/sharedfiles/filedetails/?id=3088553235
• Havoc modifier (By Combine00)
  • https://steamcommunity.com/sharedfiles/filedetails/?id=3375980903
• Shout weapon spec vet build (By Tanner Lindberg)
  • https://www.youtube.com/watch?v=fl4NhjDc3Ts