Trials of Osiris - Warlock
Voidwalker's tracking bombs and Sunsinger's self-resurrection makes it hard to pick a subclass when it comes to the Warlock, as both have their advantages.
Voidwalker's Axion Bolt tracking grenades are great for sending the opposing team running, giving you the chance to push forward and close in. Similarly, enabling the Shatter modifier will split your Nova Bomb into three, and paired with Angry Magic, the trio of Nova Bombs will track enemies.
If you opt for Lance instead of Shatter, you get a powerful long range Nova Bomb that will happily seek out nearby Guardians.
It's worth repeating the recommendation for the Prison of Elders Warlock loadout and equipping Obsidian Mind and Bad Juju if the Voidwalker floats your boat.
Aside from the Fireborn modifier that allows the Warlock to self-resurrect, the Radiance super is geared towards causing a lot of AoE damage by reducing the cooldown of grenades. To increase the amount of grenades you can use while Radiance is active, equip Heart of the Praxic Fire that reduces the cooldown on all of your abilities during Radiance, max out your Discipline, enable Gift of the Sun for an extra grenade, and turn on Radiant Will to prolong the length of Radiance. You should be able to cause quite the massacre with this set up.
If you're feeling particularly selfless, you could use the Song of the Flame modifier to reduce all cooldowns for nearby teammates during Radiance.