Just posting this for info, since this Athene method method was patched to no longer work as of Patch 2.4.2. The player being powerleveled will now receive the same experience as if getting leveled in a group with a level 70.

How he did that
You need a high level Mage, a high level Paladin and the lowbie character you want to powerlevel.
  1. All three group up and enter an instance (preferably one that is a consider number of levels above the lowbie character's level)
  2. The Paladin runs through the instance picking up all the mobs (and Holy Shocking to heal themselves)
  3. The Paladin pulls the mobs back to the start of the instance
  4. The Mage leaves the group
  5. The Paladin AoEs them down to 20% health
  6. The Paladin leaves the instance
  7. The Mage finishes them off (before they are ported out by the 1 minute timer)
  8. The lowbie character gains the same amount of XP they would have gained if they had inflicted the 80% damage.