For the most part, people play with a keyboard and a mouse. Many Lefties and all righties that I know put the left hand on the Keyboard, right hand on the mouse.
My suggestion is to put all hotkeys on the left side of the keyboard. DoTA has done a good job at that for the most part but some of the default keys for WC3 are on the right (p for patrol, H for hold position).
It would also be great if I could use my pack items with my left hand as well. Not sure if that is possible. With modifier keys its possible (i.e. Ctrl-QWASZX, something like that).
Just a thought :-) .
Its all about being quick, and quick is all about hotkeys.