I play on a full size keyboard. As a tank or DD I don't even touch my mouse. In 99% of content I don't need such fine control over the direction I run that I can't make do with forward, back, left, right, and keyboard camera turns. In nine years of playing, the only combat situation I've ever picked up my mouse for a fine camera turn was Shiva slides in E12S. Even then, I could usually maneuver myself "close enough" with just a keyboard camera turn.

As a healer my mouse is used exclusively for mouseover heals. I still turn and move with keyboard.