Apparently rogues can use Singular Focus to 1-shot anyone, as long as a low level mob or anything flagged as low level is nearby that they can attack. They put Singular Focus on an enemy player, then attack a nearby low level mob (such as a boar outside org).
Because of the insane multiplier that blizz gave us against low level mobs a little while back, Singular Focus will hit the player for tens of millions of damage. A priest I know was hit by a rogue in this way for 11 million and then another time for 18 million damage from Singular Focus outside of org, when the rogue attacked a nearby boar.