Dreadlord the Light of Dawn
Karl and I just encountered a fairly quick way to Dreadlord it up, if you get the Dark Whispers debuff in Stormwind. Grab a friend (a healy friend is an especially good idea, but we did it with a mage and a clutch Gift of the Naaru, so clearly not a requirement) and go to the portal to the Deeprun Tram. Standing as close to the portal as you can (but not going through, it will clear your debuff) turn your friend. The guards at the entrance to the tunnel will aggro, but by the time they get to you, they will only have a few seconds on target. While they make themselves look foolish, your friend should zone out to clear the debuff you just gave them. Rinse and repeat until you've dropped all your stacks of Frail Mind. Occasionally the guards will bring a ton of friends, keep your Cloak of Darkness cooldown for that eventuality.
Once you have cleared all your stacks of Frail Mind, you should have the ability to turn into a dreadlord for a minute. Go forth and wreak havoc!