Disclaimer: This is my first guide and I am sure it is not 100% optimized but I have had a lot of success with it and fun. It likely has room for improvement and I am open to suggestions. That said, the guide/build does work in the state presented and should offer a good amount of damage, sustain, and CC.
61 Warlock / 9 Necromancer / 6 Harbinger
This build is a bit different than the Pyromancer as it relies on Damage over Time abilities. Many will initially argue that these abilities will be cleansed and will therefore make it pointless for you to even play a Warlock. Nonetheless, the amount of detrimental spells this class will put down will greatly overwhelm most cleanses. It has seen great strength in 3.0 due to the Mastery Ability: Arcane Manipulation.
The stacks of arcane manipulation hitting in conjunction with Conflux after a Void Barrage refresh can cause tremendous damage. Conflux will hit for around five - six times if (death's door) procs, which hit for around 12,000 damage per hit, Arcane Manipulation hitting for roughly the same amount. This equates to well over 200,000 damage instantly with all damage over time effects and void barrage, on the first tick.
If your opponent lacks damage reduction they will likely lose half their health from a single Void Barrage.
Level 61 Mastery: I chose Final Breath for the damage it will do when your DoTs are cleansed. It will deal Ethereal Damage equal to 50% of your spell power when cleansed.
Level 62 Mastery: Healing Expertise: Causes Dark Touch to apply Neddra's Grasp.
Level 63 Mastery: Combat Alacrity will compensate for the lack of movement the Warlock has.
Level 64 Mastery: Sparking Destruction increases damage as most Warlock abilities are instant.
Level 65 Mastery: Arcane Manipulation
Dark Touch -> Defile -> Atrophy -> Necrosis -> Blazing Light -> Arcane Manipulation (if off cooldown, MUST come before refresh) -> Refresh Macro -> Spam Macro.
Wait for Dark Touch to tick down while spamming your main macro. Reapply Dark Touch and begin the rotation when it is nearly done ticking. Repeat as necessary.
The Warlock has two interrupts, one that debilitates, two fears (one instant). The single target fear has a cast bar and is only ideal if you're at the back/mid-line in relative safety. Mass Fear is instant.
How I arrange my bar:
Top Row: Neddra's Essence (Bound), Fear (Bound), Mass Fear (Bound), Choke (Bound), Aversion (Bound), Radiate Death (AOE - Bound), Consuming Agony[Macro](Bound), Skeletal Knight, Skeletal Zealot
Bottom Row: Spam Macro, Dark Touch, Defile, Atrophy, Necrosis, Blazing Light, Arcane Manipulation, Refresh Macro
#show Void Bolt
cast Death's Door
cast Draining Bolt
cast Neddra's Torture
cast Void Bolt
cast Empowered Darkness
cast Sacrifice Life: Damage
cast [notactive] contaminate
#show Void Barrage
cast Void Barrage
#show Consuming Agony
cast Consuming Agony
cast Void Bolt
Target Dot Swap:
#show salvage corruption
cast @mouseoverui salvage corruption
cast @mouseoverui deathly pall