AoE Leveling / Grinding
If your looking for a good class to AoE level with, the Paladin is my hands down choice. I realize Mages are good, and Warlocks are great at higher levels, but what the Paladin brings with high AoE effectiveness is survivabilty as well as very little down time.
From the get-go, a Ret Pally with his or her trusty 2H can solo 3-5 mobs at once, and it only gets easier as more abilities unlock as you level. Once Divine Storm is obtained, it's pretty much ridiculous at how fast you can blow through packs of mobs.
For me, at level 18-19 I was grinding the gnolls to the south of Westfall in the camps 6 or 7 at a time. Given, I had a decent weapon and gear, but nothing outrageous. I hit 20 easily in under an hour.
Every quest I had, I would drag mobs with me and burn them down once I had tagged four or five.
With the 10% experience gain from the bind on account shoulders, and the upcoming chest piece that stacks 10% more for a total of 120% xp gain, watch the levels fly by.