I was playing the AION beta over the weekend too, and last night I was thinking if dual boxing would work. I want to level up one of each class (altaholic) but I know leveling in AION will be a lot slower than in WoW, so if I can do 2 at once, things should go a lot smoother. However, I might skip making a Ranger class.

Templar + Chanter
Assassin + Cleric (assassin may need better heals than the Templar)
Spiritmaster + Gladiator

Sorcerer I will level in a group with some friends.
Ranger, probably skip, or leveling with another Cleric