Destiny 2 Warlock Build Fel Out Boy

1. Especially this season, lead with an Arcane Needle to get the strand debuff going, and to get the dark Transcendence meter moving. If you kill a strand debuffed target with Tangled Web on the artifact, you will suspend nearby enemies (and weaken them). Use your other two with Lightning Surge to clear out groups or if you need more power.
2. Slay out with Outbreak Perfected to clear groups and fill Transcendence.
3. Pop Transcendence to get your melees back and use your melees, and grenades as a mini super.
4. Keep an eye on Transcendence meter so you still have melees once your Transcendence ends.
5. Rinse and repeat.

I don't see a reason to swap off of Outbreak as it grants Transcendence, scales with harder content, provides great DPS for a primary, and fills supers.

In harder content, where you are in cover more and at range, I would think about swapping to healing rift and maybe swapping the Lightning Surge for Hellion.

For DPS, you could fairly easily swap to different weapons. You could also swap to a different build, but in a group setting, weaken may actually provide you better DPS as a group than switching to a different loadout.

With Cauterize Darkness in the artifact, Song of Flame is a no brainer. However, in many situations, you use it once to proc scorch and use Outrageous Fortune to apply more and more scorch to get a million ignitions.

I will often swap to Coldsnap if I need a way to freeze. However, I like another way to get devour going.