Prison of Elders - Warlock
The Warlock Voidwalker with the Nova Bomb super is great for taking out multiple targets at range.
For a truly magical experience, pop on the Obsidian Mind helmet and unlock the Insatiable upgrade to reduce the cooldown on your Nova Bomb.
Next, whip out Bad Juju for the String of Curses upgrade that further decreases the cooldown of your super by 7.5 seconds.
You can take it even further with the Soul Rip modifier, that also affects the cooldown time of Nova Bomb when you kill an enemy with the Energy Drain melee attack. Now enable Embrace the Void, that triggers the Energy Drain effect when you damage enemies with Nova Bomb or any grenade, and you'll be firing off your super every few seconds.
You'll also be spewing out Orbs of Light for your team like there's no tomorrow.