Basically say I wanted all the shaman to have this macro, to either dps or heal based of the main guys health %, so if he was below 70% one would heal, if he was below 50% I could alter another's macro to heal as well, and then at 30% I could have another heal. So this way if at 30% 3 shaman are healing, 50% 2, 1 @ 70. I really am not sure if this possible or not.
This is a really interesting idea, and definitely doesn't fall under automation because you're still triggering the action. Although you used to have to "trigger" Decursive too....

You can get the raw information with a combination of UnitHealth and UnitHealthMax, but as Gurlbash says it's just not possible to use that information in a conditional. From the WoW Macro Forum:
There is a very limited set of conditions which you're allowed to check for when casting spells. These are listed in their entirety in the Complete Macro Guide sticky on this forum. Since the questions are asked so frequently, though, here are some conditions you are not allowed to check for:
Cooldown
Mana/rage/energy/health
Range
Class/race/level
Presence of a (de)buff
Whether a unit is a player or NPC
Whether a unit is some other unit (e.g., whether you are targeting yourself)