I have been running a collateral damage Warlock that is all about big bangs and wiping the battlefield. I cannot overstate how much I love the Bloom ability in the Voidwalker subclass, it makes all of the Voidwalker skills 100% better. Typically I use Scatter Grenades with Bloom, which creates a cascade of explosions, and thanks to the Bloom effect any enemies killed this way explode again, easily clearing away swathes of foes. Bloom also makes Axion Bolt shine, as any enemies killed by the seekers explode, causing further damage. As for my super, I use Shatter and Annihilate with my Nova Bomb, this combination, along with Bloom, is superb at clearing away huge groups.