I don't hit a button to cast each spell, I mash a single button on my main PC, which uses a macro on each of the toons to do their actions.

Tank uses castrandom for holy shield, consecrate, hammer of righteousness, and judgement of wisdom
Healer spams lifebloom and rejuv
Shaman uses castrandom for lightning bolt and chain lightning
Arcane mage uses castrandom for arcane blast and arcane barrage
Hunter uses a shot macro for steady shot and kicking off kill command and dust cloud

One button does it all.