For heals, I'd go a completely different route.
But go with whatever makes the most sense to you.
No one else knows what is easiest for you, or what you need for your set up.

I personally used to go with a few keys for the healer which are assist based.
IE, a priest has:
/assist Tank/MasterToon
/castsequence [target=targettarget,help] [target=targettargettarget, help] reset=8 Penance, Flash Heal, Flash Heal, Flash Heal.

/assist Tank/MasterToon
/cast [target=targettarget,help] [target=targettargettarget, help] Renew

/assist Tank/MasterToon
/cast [target=targettarget,help] [target=targettargettarget, help] Power Word: Shield

If you were using a Resto shaman for healer, you'd likely go with Earth Shield, Riptide, Chain Heal and Lesser Healing Wave (pvp) or Healing Wave (pve).

These work, because whatever the master toon is killing, your priest is targeting.
And then the heal goes to whoever that creature is targeting, which is generally your tank or someone else tanking (even if its a DPS who overnuked).

In addition to assist heals, I used to go with toon specific heals.
This works just like the /cast [target=party1] Flash Heal.
Except they read /cast [target=Toon1Name] Flash Heal.

If you have the Jamba addon (very much recommended)...
You have options for a toon to announce when they're hit.
They also have options to announce when they drop below a configured hit point percentage.
Instead of generic buttons here, you want specific instructions.
The default is something like "Help I'm hit". And "Help, I'm below xx percentage".
These come up as raid warnings.
My priest has five wow macro's. Each is on it's own keybind.
The macro is something like:
#show Renew
/cast [nomod:alt, target=ToonA] Renew; [mod:alt, target=ToonA] Flash Heal
Within Jamba I've changed the "Help, I'm hit" to read, "ToonA is hit, press F8".
I've also set the health percentage to 66%, with the message, "ToonA needs a heal, press Alt F8".
Pick the keybinds you find easy to press quickly.
*Edit* - You do not want to use "Push to Characters" here, you want each toon to broadcast their own specific keybind. */Edit*

I still use the assist based heals, because they're fast and easy and don't require thinking much.
I'm moving towards Mouse Repeater regions, via InnerSpace (and ISBoxer Toolkit).
Basically use something like Vuhdo or GridCustomLayouts, to display the party in a fixed order (alphabetical) on every screen.
Then with Clique (for Grid) or Vuhdo does it in one addon, configure a Left Click to be Renew and a Right Click to be Flash Heal. (Can also use modifiers, like Alt + Left Click = Greater Heal).
Then use a "Mouse Repeater Region", so when I click on the Vuhdo/Grid window, it sends the click to the priests window in the same position.
The priest is of course set up to heal the unit frame it is clicking on.