Two things:

http://us.battle.net/d3/en/blog/4963...4_19_2012#blog

See you all in the lagfest this weekend.

Also, there's something called "elective mode" which you can activate that lets you assign hotkeys and MBs to ANY skill you have. Attaching certain skills to a particular hotkey or MB is just a way to help utterly confused noobs, I suppose.