Indignatus crit zealot
 Zealot Build - Warhammer 40k: Darktide 

The crusher's single target attacks (and push attack) have a significant finesse multiplier now, which lends itself well to zealot's crit chance bonuses. Combined with the huge safety net that the special attack provides, the unyielding damage bonus on heavy 1 for monstrosities, and the great cleave on your horizontal attacks, you end up with a very versatile and effective melee pick.

Attack combos

Horde clear: 

light > heavy > repeat, or start with a push attack, then heavy > light > repeat

The push attack (PA) has the same cleave as light 1, better finesse damage on first target, better armor pen, and worse cleave damage. 

Single target - unyielding (monstrosities, bulwarks, reapers):

heavy > block cancel > heavy

Heavy 1 has a ~20% damage bonus against unyielding, so is worth spamming over other single target combos.

Single target - not unyielding:

heavy > light > repeat

From testing, the above yields slightly better DPS than heavy > block cancel > heavy against crushers, maulers, ragers, etc. Spamming push attacks against crushers will technically yield better DPS, but push attack has much less stagger and so is a lot less safe

Against elite packs: spam special + light 1, throwing in special + heavy 1 or special + PA when it's safe.

Other tips

• The special attacks have no negative side effects. They just increase your damage a bit (20%) and add a small AOE effect that deals a little damage and a lot of stagger. If you're walking up to a crusher, etc, and have the time: may as well activate your special to deal a bit more damage. 
• It's also a good idea to activate your special when ulting into a group of enemies. The AOE deals a pitiful amount of damage, but it does deal damage! This means each enemy hit (and thus crit) by it counts for on-hit effects. This includes: stacks of blazing piety via fury rising, bleed stacks from scourge, and most importantly: cooldown reduction on crit from invocation of death. When ulting into a dense enough horde, you can easily refund your entire cooldown.

A few notes / justifications for picks here:

Thy wrath be swift: Unclear if this is a bug or intended + a bad talent description, but this talent currently makes you immune to stagger from ranged enemies as well. This is hugely beneficial for surviving a lot of bad situations.

Blades of faith: We really don't have a choice here. Reaching either other grenade slot would have a major cost for the build elsewhere, and the crusher's special does a lot of crowd control work anyway. Once you get used to them, they're excellent anti-special tools. Headshots are one hit kills for all specials except mutants, as well as both types of gunners and shotgunners. A good fallback when you don't have time to reload your revolver or are out of ammo.

Ranged weapon (revolver): The crusher is so versatile that I don't really feel like there's any holes left to fill besides mobility and special sniping. Revolver brings both. Laspistol is another solid option, though.

Unarmored damage on revolver: This hits the 1 shot body shot breakpoint for snipers as long as you have a good damage roll.

Block efficiency on curios: since we don't run a crowd control grenade, when trying to revive someone without help, I'll usually throw out a special attack with the crusher and then start reviving. Block efficiency just gives a bit more padding here in case enemies make it back to you before the revive finishes.