Knives Out
 Ogryn Build - Warhammer 40k: Darktide 

This is another fun weapon layout for Ogryn that can definitely carry heresy public lobbies.  A lot of this guide is in common with https://darktide.gameslantern.com/builds/dfdebc74-116e-48d2-8e59-8f590fd87c8b/heresy-pub-ogryn

Weapons:

The MK IV Cleaver was my first favorite weapon on this big guy.  The light attacks have a ton of bonus headshot damage but it'll take a bit of practice to hit heads with them, and depending on the angle you might not be able to.  On the other hand, they come out incredibly fast, making this one of the highest DPS weapons the ogryn has access to against anything other than carapace and maniac armor.  Bonus vs infested comes in handy both vs pox walkers and dogs.  Vs hordes you will typically be comboing either light 1 or the push attack into heavy 2, where heavy 2 will be doing most of the killing.  Vs lone enemies the light headshots on a wll rolled dagger will kill anything except a the scabs in heavy head armor.  Bonus vs unarmored will allow it to 1 shot all dregs.

Any of the cleavers are really strong on Ogryn, and many prefer the Bull Butcher MK III for it's sweeping, horizontal, head level attacks.  All I can say is that when you get any kind of knife with Savage Sweep and Slaughterer, hordes will no longer be a concern for you at all.  What sets the MK IV apart is the speed of it's single target light combo, which can let you shank a shotgunner in the face faster than any other.  Vs mixed hordes, you will still want to use the light 1 heavy 2 combo, which is perfectly adequate if not quite as horizontal and head level as the bull butcher.

The niche of the MK V is that it has no vertical heavy attack, so you can just chain heavy attacks to deal with hordes.  I find the push attacks help make hordes safer to deal with, and if you mix those in you'll always get the sweeping heavy on any cleaver.  It's light combo is substantially slower than the MK IV.

You might be tempted to use the Confident Strike or another blessing on your cleaver to increase your ability to get toughness back in combat.  I don't think this is necessary on the cleavers because you should be killing so many enemies, and you should be mobile enough, that you will get a ton of toughness back from that.  It's not in the middle of a horde that you will need to regen toughness, but when shooters are dinging away at you all over the place, and in that situation you won't be getting any value from the toughness regen blessings on your melee weapon.

The Grenadier Gauntelet if well rolled should hit 1 shot breakpoints on dreg gunners and all shotgunners if you land a headshot (purpose of vs. flak damage), but take 2 shots otherwise.  Shattering Impact will make this solve crushers incredibly quickly.  You can completely ignore the melee attack stat of the guantlet, especially since you won't proc bleeds from them.  Ammo will also never be a concern unless you don't have a veteran with you.  Try to find one with high blast damage and penetration.

The Rumbler is a fun alternative ranged weapon to pair with the cleavers, since it can handily deal with carapace as well.  It provides quite good area suppression vs gunners and shotgunners, but kills them far more slowly, since most of the damage will come from the slug itself which must be reloaded every shot.  You'll often need 2 shots to kill bombers which can be quite a pain.  But the benefit is that you only need to peek your head out for a moment to get a shot off that will potentially suppress multiple gunners and kill one.  You can also whip out the rumbler just to shoot at your feet if you're getting swarmed, and you'll have a bit of breathing room in a moment, which doesn't really work with the grenadier gauntlet.

Perk discussion (Below section is the same for all weapon combos)

* Lynchpin: If you're concerned about regenerating your toughness in rooms full of shooters, this is a major part of the solution.  You won't always have enemies in range, or want to use heavy attacks.  This allows you to hide in cover or just run around sliding and regen your toughness faster, and is a massive boost to your teammates as well.  It is the only one that remains useful when you have your heavy bolter out.
* Heavyweight: this perk affects both melee and ranged.  Often you'll be able to prioritize ogryn enemies to do extra damage.  You don't really have to worry about tanking these hits to res an ally here
* Towering Presence: other options are strong here, but consider the amount of ammo you will get from being in range of your veteran more often, the amount of damage resistance from being in range of your zealot, and the amount of toughness regen you're providing your team with Lynchpin. And consider also situations where you can link the team together and provide those buffs to everyone. This is by far the safest choice here, and it emphasizes mitigating the risk of getting a team that won't stick together closely.  There can also be times it's advantages to adopt a loose formation where you can keep everyone in coherency.  Bullfighter can let you charge into every elite pack you see and mostly keep charge up anyway, but it can be unnecessary if you have a psyker on your team with psykinetic aura, where towering presence becomes even stronger.  With the heavy bolter you won't want to open a lot of elite packs with your charge anyway, as it will put you out of position to maximize your DPS.
* Hard as nails This makes it much safer to pick someone up in the middle of a fight, not being conditional on bleeding enemies near you.  It's guaranteed to apply when it counts the most, but disablers. If you're the last man standing you can tank a lot of las fire with just your HP, especially if it's coming from a reaper!
* Raging Bull: Neither this nor Knife through butter are very effective, but raging bull at least lets you use more frequent attacks which will apply more stagger and DPS.  Even if you use the heavy attacks fully charging them just takes too long to be worth it in most scenarios, and it's nice to get a substantial bonus even while using lights.  Even with the shield and high cleave you won't notice a lot of extra models dying in the psykhanium from Knife Through Butter
* Nonstop Violence: This is nice to have with lynchpin, since you don't have a very easy way to get a lot of toughness back quickly after you've been trading for a while with the bolter.  This enables you to have less downtime.  Unstoppable is also decent, but you shouldn't use it to make long distance charges away from your team.  Charges should generally end within coherency of your team to be safe.

Ability Usage

Don't just charge into every pack of poxwalkers you see.  When they are all clumped up they are easy to kill with melee or other options.  Your charge doesn't have ammo, but the cooldown means you want to have it available for situations where you need the charge to save a lot of HP or other resources.  With that in mind, here are some decent use cases for your charge to use as examples.  This list is obviously incomplete:
* Someone is getting thrown around by a mutant in a non-critical situation.  This will prevent damage to your teammates without costing a grenade.  If you can kill the mutant with your heavy bolter beforeyour teammate takes damage that would be preferable.
* You've been trading with ranged enemies with the bolter and your toughness is low.  There are some elites that have gotten in range and are about to attack your allies.  Prevent damage from them while 
* You're fighting a boss.  Use it as early as possible to stun them for your team to get in the DPS, and maybe you'll get it back before the end of the fight as well

Grenade Usage

Your grenade is more limited resource than your charge, and far more limited than ammo.  You should conserve them for even more critical situations, when shooting something would take too long.  Notably they 1 shot mutants and snipers, but you don't have enough to use them on every mutant or sniper.  Save them for situations where a mutant spawns and your team is all occupied dealing with other things, or when you are unable to give the mutant your full attention because of other pressing concerns like a flamer or dog after you.  They can also do a ton of boss damage, just line them up carefully to be sure to hit a weakspot.  Because they are so damaging and limited it's worth time making sure they connect properly.

The curios

As an ogryn your HP pool is massive, it's silly not to take advantage of that by stacking as much HP as possible with curios.  You almost always have an option to disengage or charge when your toughness reaches zero, and having high HP will allow you to take a ton of chip damage through your toughness without issue.  Stacking this with the damage reduction if you're the last man alive will allow brush off attacks that would 1 shot other characters, especially from enemies like crushers and reapers.  Extra wounds are terrible on the ogryn because you already have 1 more than everyone else, and if you're dying that many times and you have a bad team it's gonna be game over regardless.  The extra HP will let you never have to use those wounds.

The damage reduction you can get on curios is very strong on the ogryn also because they multiply your already large effective HP pool.  Consider your own playstyle and the enemies you take a lot of damage from.  I like to be able to stare down lots of gunners and just shoot them all, so a bit of damage reduction from gunners stacks nicely with all my other innate DR.  If you are bad at dodging bombs you might prefer that one, or DR vs snipers if you often fail to dodge their shots.

Toughness DR is probably the strongest curio perk.  Whoever did the numbers on the toughness DR perk compared to the increased toughness base stat was not good at math.  Toughness DR is far more valuable than % increase in total toughness because it also effectively increases your toughness regen from all sources.

Ultimately until you're rich you'll probably have to take what you can get when it comes to curio perks.