Starcraft2: left/right + wheel + shift + ctrl FA: left/right + wheel + shift, I would use ctrl but it is not really needed in most cases as unitgroups are very rare.
3 Every day, in some games 5. I usually bind voice chat to middle click. The other buttons are reserved for cycling weapon racks in MWO. If there is a use for them, I will use them.
LMB, RMB, MMB, back/forward and numbers 1-12 I use on the mouse, with the back/forward normally being map pings and the numbers used for control groups, I like being able to do that with my thumb. (so that's 17 buttons )
Right, left, scrollwheel to zoom in and out and hold middlemouse(well pushing down scrollwheel) to rotate camera with mouse movement.
Remember, the scrollwheel click would be considered the 4th. scrollwheel itself is 3rd and is quite common.
Depends on the game I'm playing. When I played MMOs like SWTOR, I used all 17 buttons on my mouse pretty heavily in PVP. When playing SC2, I use most of the 1-12 buttons to select assigned groups.
