I would say one Sunsinger Support Focused. Keeping Ignite active 24/7 will allow the rest of the raid to be dealing huge damage and with 2 it's unlikely to stack 1 Sunsinger (Ignite/CD spec) 2 Defender (Unlocked so can swap for increased damage or shields) 1 Striker (Shotty/CC spec) 1 Bladedancer (Replenish super spec for thralls etc) 1 Voidwalker (Vortex specced for CC) (This warlock can switch to Sunsinger if there is more solar needed) You have to take into account the elemental damage. Your build only gives one void damage and that's a Defender, not enough imo.