If you have the money to spend, a gaming mouse is a godsend. I have a Razer Naga and it has the 1-12 keys mapped to the 1 through equal sign keys on the keyboard by default. This essentially puts all of my abilities + camera movement in my right hand while I use wasd to control my movement with my left. You can also set up additional hotbars with shift/ctrl/alt + numkeys.

But like others said, it's not mandatory to have one. It's just so much more convenient.