Something else you can try is to have shift/ctrl/alt modifiers.
eg.
/cast [target=Rou,nochanneling,mod:shift] Rejuvenation, Lifebloom
this will cast Rejuv when shift+5 is pressed, and lifebloom when just 5 is pressed.
or you can have a button that is tank heals only, and use the modifier casts or castsequence without the comma gaps.
another example; I have '3' set to do PW:S on press, and shift+3 Prayer of mending.
shift+4 is binding heal, and 4 is flash heal. I have G2 as penance, but ctrl+3 could do it just as well.