WOW Power Leveling: You can kill more mobs in less time than with traditional one-mob-at-a-time XP
The Kill: The mobs have arrived. The tank has the mobs. Now it's time to kill. If you are doing polearm parties, the pole-users usually start attacking right away. This builds aggro, and, with WOW Power Leveling Vampiric Rage, helps restore their HP.
If your group is Hate tanking, however, while the tank pulls agro with his AoE hate skill, a Sorcerer or Spell singer in the group casts an AoE sleep on the mobs, giving the healers a breather to fill the tank’s HP up.
At this point, the process is simple: hit them all, and kill them fast! Pick up your loot, and repeat.
Advantages over Traditional Experience: The basic advantage of AoE experience (XP) is twofold: Fast, and cheap. If your XP team gets good at pulling, you can kill more mobs in less time than with traditional one-mob-at-a-time XP.
So, the more mobs killed at once with an AoE skill, the more efficient the skill gets.
Plus, the AoE skills spread out over several mobs save money; soul-shots and spirit-shot costs are spread out over many mobs at the same time, improving the cost per kill ratio, saving the party money.