I'm saying, don't make a macro like this:
/cast Spell (rank 4)

And don't go:
/cast Spell (rank 2)

Just go with:
/cast Spell

It will automatically pick the highest rank that will land on the target (some buffs will not land on toons that are much lower like say the priests Spirit buff on a level 4). Regardless of the rank it chooses, you will be charged mana for the highest rank you know.

For heal spells, they should land on any target irregardless of the targets level; if they don't you have some kind of a bug.