@Rowan
Idk if anyone has mentioned gaming mice yet, but they're a game changer imo. I can do most of my tanking rotation using my 2 extra mouse buttons alone (using shift,alt and ctrl modifiers)
I use: http://www.amazon.com/Microsoft-HKA-00001-SideWinder-Gaming-Mouse/dp/B000TTQFIS...Works great for Swtor imo.
On a side note you can bind scrolling your mouse wheel up & down. I use alt + mouse scroll up to charge and alt + mouse scroll down to grapple.