You all need to turn on Elective Mode if you haven't already under Options > Gameplay. I read it and took it as being able to just bind buttons to different keys. I was terribly wrong. Elective Mode's best feature is that it allows you to select multiple skills from the same branch (Like Primary, Secondary, or any of the 4 class specific groupings).
For instance, I don't use my secondary on my Witch Doctor or Barbarian. So instead of having the slot given to a useless skill, I was able to select a skill from a tree already in use. Incredibly useful.
Also, looking around, from what I can tell, the biggest thing to look at to increase your damage is weapon damage, followed by added damage, followed last by whatever your main stat is (Int for Wizards and Witch Doctors, Strength for Barbarians, and etc.). Useful tip.