Crust Shredder
 Veteran Build - Warhammer 40k: Darktide 

According to folks on reddit pox crusted skin in Havoc is carapace. IMO The Havoc difficulty levels seem to be very lazily done and doesn't really consider how the the sum of conditions is greater than the whole often resulting in even maps in the 20-30 range being unplayable by level 40 players.

Hopefully this build will help a bit - it is optimised in the Psykanium to take down crushers and pus hardened skin enemies. It will kill a crusher with headshots in 12+-5 shots (depleted ammo, obviously more rounds are fired but Shock Trooper nullifies crits) assuming infernus finishes them off so it's highly ammo efficient.

The absolute core of this build is Onslaught and Weak spot + Deadshot + Shock Trooper as they will turn your recon lasgun into a tin opener. 

The other buffs you can play around with, I'm still undecided about the keystone really being much benefit due to the iffy weakspot hit detection.

You do need to learn how to minimise incoming hits, this is not a tank build and I've found more wounds is preferable as a death is more of hindrance to the team for the veteran than being downed.

Camouflage works better than the weakspot bonus because it's guaranteed to stack if you can find a good spot in cover - make sure you learn to use dodgy when crouched. Use the Long Range Assassin if you prefer but I find the weak spot hit bonus doesn't fire properly even with direct constant hits so something janky is going on in their code, maybe it's some kind of debuff for the recon lasgun IDK.

You can drop the keystone and spend those 3 points elsewhere (ie for stealth) build the same build with stealth if you prefer and drop the keystone and it will still be about 14+-3 shots. 

I tend to play both Voice and Stealth even in high level Havoc - if there's another Vet with voice at high levels then stealth can get you out of a bind if the whole team goes down so it's useful to have a loadout for both.

You can drop the 3 or 4 talent points needed by Onslaught if it's not pox encrusted but I've found it's better to keep it as the number of crushers goes up in higher levels anyway.

With 2 charges to rescue them: run away if they're dead/screwed then use stealth 1 circle back round, shoot their guards and wait for them to advance on you then use stealth 2 to get to your team and revive 1 or 2 and pray. Sometimes it's better to do this than try to revive on the spot if you know the respawn point and can get clear of the melee e.g. you're absolutely covered in fire or pox gas.

Final thought: if you play other classes then understand the veteran is going to be your main DPS and you need to let them hoover the ammo because Fatshark's ammo debuff in Havoc is ridiculously unfair to the vet class - ie psyker has infinite ammo no debuff and zealot / Og are mainly melee.