Look for the enemies to start up a power blow and block it to get a chance for a nasty retaliatory strike, and charge up your own power attacks by holding down the mousebutton.
While both the left and right mouse buttons do require a solid press, they're large and responsive all the way up to the apex of the mouse, and there's actually only a single spot (on the extreme upper-right-hand corner of the right mousebutton) where it won't actuate if pressed down.