I have written a guiide to leveling as affy. Affliction rocks to level. Especially on gathering quests which as a boxer we skip but...
Generally what I do is I cast the three instanst dots and run onto the next mob and same thing. Next thing I know I have 8 mobs that I am killing at once. With 3 you would be a force to reckon with. To me that would be a better build then demo.