I did a little test run of 1 paladin + 4 warlocks that was pretty fun. Voidwalkers tank 4 different targets then the warlocks DoT up each one at a time. By the time the 4th is DoTted the first is dead and that void walker is moved on to another target who gets more DoTs added. The paladin just keeps the Void Walkers alive through everything and keeps blessings on the warlocks. It was really quite effective for taking down outdoor elite spawns and instances. Plus you have the res there when necessary.