One thing I have found that helps is using the same keybind across different characters for similar abilities e.g. On all my characters, an interrupt ability is on one of my mouse thumb buttons, damage reduction ability (e.g. Deterrence, Shield Wall) on Shift-T, Burst of speed (Worgen racial sprint, heroic leap, PW:S (talented for speed boost) on Shift-E.
It is absolutely true what others say that setting keybinds will take maybe 30 mins to an hour to get used to when you have to remind yourself what the keybind was but eventually it'll become 2nd nature and you'll be glad you did it.
I main as a Hunter and on dark shamans, if I've found myself on the wrong side of a badly placed wall, it's not unusual for me to use engi belt, run, jump, turn 180, hit disengage & deterrence, turn 180, land & continue running. This wouldn't be possible with clicking. There are many more examples that could be given.