On DDs and tanks I play keyboard only.
On healers I use middle, nav forward, and nav back mouse buttons for mouseover heals, and make sure Sprint and Surecast are bound to mouse buttons as well.
More detailed keybinds:
You definitely should not use all twelve keys from [1] to [=] if you don't have both hands on the keyboard. This is because of Fitts's Law, which states that the difficulty of pressing a button increases the farther you have to move to press the button. If you only have one hand on the keyboard, you have to move your hand an obscene distance to be able to reach the other end of the number row which will make accurately pressing those buttons difficult, and then you have to move an obscene distance back to your resting position which will then make pressing should-be-easy buttons difficult while you reposition.
If you play with left hand on keyboard and right hand on mouse, you should limit your controls to this green section of the keyboard, though you might need to extend into the yellow section on some jobs:

This minimizes left hand movement, which will increase input speed and accuracy.