i might have figured it out
this might work (again, tank/main is set as focus)
/castrandom [target=focustarget, help] Regrowth, Rejuvenate, Lifebloom; [target=focustargettarget, help] Regrowth, Rejuvenate, Lifebloom
if i target an ally it should cast 4 random heals on them (1 per nontank druid). if i target a mob, it should cast 4 random heals on that mob's target.
i just had another cool idea; have 3 druids do the random heal on the mob's target, while the 4th druid cyclones that mob. a good "oh shit heal that guy and cyclone the guy hitting him" effect.
i'm thinking i should have a button that does /cast [target=Ghostbusterz] Lifebloom
that is, later on, when i'm tanking heroics and such, i'd have to be more deliberate with stacking hots.