So I was playing the mission Genesis, and by killing off the Promethean’s fighting the Covenant and activating the bridge that Exuberant makes, I managed to set up a scenario where the Warden ended up fighting two Covenant piloted Wraiths. They duked it out for a while, and the Wraiths won in the end. The moral is, why kill the Warden yourself when you can just get other enemies to do it for you? Could also be a useful strategy for Legendary.