The Alpha Primus (v5)
 Skitarii Build - Warhammer 40k: Darktide 

I think this will prove out to be the strongest build for your average havoc player. It has plenty of DR, solid team utility buffs, Chordclaw spam 5+ in a go, and the servo skull blitz set which is very useful while not putting a lot of pressure on blitz economy.  The objective of this build is, like most "meta" builds to optimize as much as possible for team utility while also getting as much damage as can be managed. AOE damage is considered a priority wherever it can be found. Team toughness support is is taken over damage nodes in some cases. 

V2 Notes:
Sacrificing Adaptive Combat Calibration does reduce DPS into hordes, its modest. about 4-6 seconds. Not worth worrying about. 
Taking Noospheric Command is super worth it and massively extends ammo economy to the point that dropping Ammo-Cell Augury is viable.
Electro Strike Conduit is a huge boon for safety and I really like taking it on this tree. Its very worth it. Can be triggered on purpose with light spam transonics reliably. 
Capacitory Limit Override has been dethroned on some very tight margins by Hydraulic Impact. 

V3 Notes:

System Shock: Having tested system shock I found that the rending from redlines is more consistent and my shock application options on this build are basically just Electro-Strike Conduit...I felt that not taking this node was the right choice. 

Augmented Power-Cycle: unfortunately I cannot identify any specific value proposition for Power Overflow. It just never feels like its doing anything so I have moved to better capacitance regeneration instead with Augmented Power Cycle. Overall my output is better in a game and thus there's less pressure on the team. on the whole medicae skull, Voltaic Restoration and Data Sensor Protocol make up the sum of the support on this hybrid build. The rest of my work is hereticide and debuffs. 

FLAME SKULL:

I love the spinny purgator skull. Its useful in a lot of situations for smoothing out a run. Also can solo hexbounds. In any case - many people don't like this so here's my recommendation for other solid talents in no particular order: 

Target Prioritization Psalms
Evasive Servo Recovery
Shockline Breach Protocols
Adaptive Combat Calibration
Adaptive Combat Engram
System Shock
Surge Extension

Arc Maul vs Transonics: 
There are 3 reasons to choose the Transonics in this build over the arc maul, but it works fine with the arc maul for what its worth. 

1. Improved mobility characteristics give the Transonics an edge on an otherwise slower moving and dodging class. This gives the class a real boost in survivability and positioning. 
2. Crit rate on transonics is big. Transonics crit a lot more than Arc Maul which provides crit synergies.
3. No off state. Arc Maul when on is stronger than Transonics especially into hordes. But when its unempowered, which is less uncommon than I thought, Arc Maul suffers from poor TTKs into all targets. Transonics are reliably solid into any target group and any gaps in horde clear are cheaply made up for by the odd chordclaw. 

Curios: 
I'm not sure about that 5% health. Could be more combat regen.