Lots of people claim AOE power leveling is the best possible way to level at all times. I haven't found this to be true. However, there are certain spots/levels when AOE grinding is the best and easiest way to level. I haven't find many other AOE spots in which I consider viable. However, designing your talents around AOEing slows you down for obvious reasons; you always will need a priest to level at maximum speed, and it's not solo. You don't want to cast a fireball when the monster has only 10% health left - because your fireball's normally do around 20%. Get the idea?

 

Knowing how much damage your spells do helps A LOT. This doesn't only help in grinding, but with PVP too. However, I must say that if you have a priest, then AOE power leveling becomes a much better possibility. I would suggest getting a UI that displays the opponents (monster/player) HP as a percentage. This makes it easier to familiarize yourself with damage. I suggest using either Nurfed's UI or CT Mod. Personally, I use CT Mod and some of the Nurfed add-ons together. The general point to knowing your mage's damage, is optimizing your mana use.

 

Fastest and most entertaining (you have someone to talk to, joke around, etc). The only downsides are finding someone to preform this task for you. There's no way to get rid of it when power leveling. There's ways to deal with it, fortunately. Survivability is why solo AOE grinding is flawed. Little quests are done. Probably the best form of power leveling. It's important to note that dying decreases your exp/hour rate A LOT, so if there's a good chance of you dying, it might not be worth the trouble at all.