You could do modifiers, use the same 5 keys you do now, but mod for each group. Might get dicey though. In Raid healing though, wouldn't it be better if you just focused on healing the tank? You're gonna have other healers picking up the slack. You could also put in a targettarget macro to heal whoever the mob is targeting, as a sort of catch-all button. I do all my priests healing with focustargettarget, and a separate button for AoE, and one to heal just my tank specifically. The less buttons the better.