Here's a double special weapon build Hunters can use in Deep Dives
Double special build are popular because primary weapons in harder content feel too weak.
The issue with double special is ammo, but the right build can manage that. This build is all about creating special ammo on demand with Special Finisher.
You'll need 3 armor charges and you'll want to build up those armor charges quickly so Stacks on Stack and elemental charge fixes that problem.
Plus ways to create Orbs (Reaper, Solar Siphoning) and Void Breaches (subclass perks) for 2 ways to build armor charges.
Titans and Warlocks can make adjustments to use this too