Some Idiots Havoc 40 Support Zealot [Martyrdom]
 Zealot Build - Warhammer 40k: Darktide 

This is some idiots guide to Martyrdom Support Zealot as of the Zealot rework. Yes, Martyrdom, not Piety. Functionally I prefer this setup because my personal opinion is that Zealot is currently better played focusing on DPS rather than trying to be a pure support like they used to. With this build I've achieved highest damage at Havoc 40 numerous times while also being able to quickly revive/save teammates and providing gold toughness/suppression on demand with Chorus. Before we start, this build demands you remain at low HP for the duration of the run. Blowing yourself up, standing in fire, getting shot by a sniper etc... are all viable ways to take damage without accumulating corruption. You need to be at low HP to get any benefit from Martyrdom and to get CDR for Chorus.

For starters, Zealots role right now is not what it used to be. With CDR nerfs and nerfs to Duelist damage, the old Chorus bot playstyle where the Zealot stayed afk while investing little into offense is mostly dead. Your role would be better filled by your team taking a second Voice of Command veteran with a Power Sword who can deal melee damage just like you can while outputting higher gold toughness uptime. What do you do now instead? Damage. Lots. Any second you're not using Book you should be playing as your teams second DPS role in melee, pumping damage equivalent to your Psyker. Your book is now relegated to an emergency button being a strong tool for creating space, crossing gaps with your team in open arenas/hallways, approaching gunners and ramping your teams damage into dense armour waves. It's by no means a bad ability and those saying it's dead don't actually know how to play the game, it just can't be spammed as frequently as it used to so it can't carry the person playing it to the same degree as before. Zealot isn't a bad class, you just need to adapt how you play it. You're not casting Chorus as often as you used to so you need to enhance everything you're doing while you're not using it.

Below is some generic explanation for some choices in the build and 

Regarding CDR we're taking Martyrdom's own special CDR node called "Martyr's Purpose". The reason we're taking this compared to PCT is it's active permanently rather than requiring constant melee combat, allowing for you to regen FoTF charges while kiting, moving between spots with your group, moving between gunner packs, approaching, fleeing, you name it. PCT will be generally better into Melee seeded runs, however if you lose the gamble and get a Gunner seed then you're frankly just going to have a worse time. Martyr's Purpose only gives you marginally less CDR in return for it having basically no conditions for access provided you're playing this build at low HP like you're meant to be. Considering we still have to access Martyrdom and Riposte anyway, choosing this allows us to save a point that'd otherwise have to be spent pathing through Punish Impiety to still get access to Martyrdom if we went for PCT as well. It also allows you to continuously benefit from it while taking a step back to use your flamer, which this build encourages more cause of us taking Anoint in Blood.

You might have noted we've entirely skipped both Bleed for the Emperor and Restoring Faith. Why? Cause they're frankly unnecessary and actually counterproductive sometimes to our plan of skipping to low HP and remaining there. While they both make the build more forgiving, especially Restoring Faith, this is still 2 points that are mostly unnecessary provided you're playing correctly and could be better used grabbing more useful talents elsewhere. Restoring Faith can sometimes regen you above your final wounds, getting rid of Martyrdom stacks and making you have to find another red barrel to injure yourself again or just suck it up and deal with having less damage/tdr/attack speed. It also really doesn't regen enough to be worth it imo. Bleed for the Emperor is also just bad? It slows your ability to damage yourself down to that 25% hp threshold,  and you're only getting value out of it for maybe a hit and that's it. If Martyrdom gave you any buffs at high HP and you actually got value out of it protecting you for every one of your 6 wounds? Yeah it'd be pretty nice. But  when playing properly you're only effectively playing with 2 wounds at most after a UD reset so it's just a pointless talent.

Providence is something that got added with the Zealot rework and allows for easier revives and netter saves, which we're further buffing by taking an extra revive speed node on one of our curios. Providence is something you're nearly always grabbing cause of your build path and is just nice to have for the occasions your team struggles. 

This build has more flex points than a Charge build due to the action skill having less needed investment, so we've used them to take both Anoint in Blood and Enemies Within, Enemies Without. Anoint in Blood enables stronger Flamer play due to its damage buff also affecting DoT's. Not much to it. Enemies Within, Enemies Without is a comfy option that after the Zealot rework got buffed a lot. Regenerating 7.5% per second that can be triggered by being around only 1 boss enemy is a considerable amount for such an easy condition and allows you to absorb/ignore more chip damage than you normally would, and is enough to allow you to stand in pox gas as long as you have some DR/TDR sources stacked while not taking corruption damage. It's not 100% necessary but feels nice to use, making the build feel more consistent and giving you multiple sources of toughness regen. You can forgo either of these for other options depending on how you like to play, picking up stuff like Backstabber, Good Balance, Unseen Blade, Punish Impiety etc...

Onto weapon discussion:

 Out of all the classes Zealot has the least utility to give their team especially with CDR nerfs, so dealing lower damage than everyone else just to be a more infrequent VoC veteran is pointless. Mk2 Relic is arguably one of the 2 best options in Zealots kit for their new role, with great horde clear, cleave, single target, boss damage etc... with the only downside being sub par mobility that can still be mitigated somewhat.

As for its blessings/perks we're taking Cranial/Rampage and Unyielding/Carapace. Unyielding/Carapace should be self-explanatory but its basically just cause you need the extra damage to kill bosses, crushers, ogryns etc... and ramp your damage further. As for why we're taking Cranial compared to something like Wrath for the extra cleave? With the Zealot rework we're taking Against the Odds that gives us 50% cleave into any horde scenario which mitigates the need for cleave on our weapons compared to before. Even into Havoc 40 enemy hit mass this is still a viable decision to make as I've tested, as you're still likely to kill hordes at a similar rate especially with the higher Energized uptime from Cranial. In return for dumping horde clear slightly you're getting a lot of single target DPS which is especially useful against modifiers like Rotten Armour where Wrath was practically a dead perk as well as making you delete bosses even harder than before. Until modifiers like Moebian 21st and Rampaging Enemies (due to their higher hit mass) come back into Havoc rotation this is a viable setup, and once those return you set another relic blade with Rampage/Wrath instead and switch as needed.

As for how to use the Mk2 Relic Blade it has a few main combos:

Horde Clear Fast: Heavy > Heavy > Light > Heavy > Light > Heavy etc... (Access it from the 2nd heavy then loop that 2nd heavy into lights.

Horde Clear w/ Stagger and better energized economy: Heavy > Heavy > Light > Push Attack > Repeat (Can also start from push attack)

Single Target for Basic Elites (stacked Shotgunners, gunners etc... that die quick): Light > Light > Block Cancel > Repeat

Single Target Main: Light > Heavy > Heavy > Loop Heavies (Uppercut does marginally more damage for some reason. Needs to be aimed slightly for consistent headshots)

Switch between these as necessary. Your highest single damage attack is your sprinting stab which you don't actually have to be fully sprinting to activate. If you briefly hold sprint and forwards while looking slightly down to an angle while holding heavy attack you'll immediately enter a stab attack without having to commit to sprinting forwards, allowing you to prepare it immediately for hitting something durable in a weakpoint. You can block cancel after it to immediately be able to do it again. You can also use this attack to hit a BoN's weak point from the front if you align the attack right, giving you high damage without having to flank behind the boss that'd put you out of position and in the range of its AoE attacks.

As for moving around with the Relic Blade you can move-tech by holding the Sprinting Stab attack, letting go for the thrust, switching quickly to ranged then back to the sword, then going into another Sprinting stab, repeat. The move gives you some additional speed compared to just sprinting with it out normally so it's usually always worth doing when you remember to.

On your Flamer you can run either Flak/Carapace or Flak/Unyielding. Flak/Carapace will do better into Rotten Armour, Flak/Unyielding is mostly suited to when this isn't in rotation and you're running a Overpressure/Blazeaway setup. The former is better into general havoc gameplay dealing with things like Crushers easier while the latter will get the highest damage to both hordes and bosses.

Use the Flamer for situations where melee with the Relic Blade is too risky, multiple stacked up bosses, being a replacement for your Psyker if they go down or can't keep their Purgatus staff going etc... can also be used as effective suppression against gunners/reapers.