I use two methods.
Some of the spells are like your method 1.
My assist is target=targettarget, with my casters targeting my tank.

/cast [help, target=targettarget] Lesser Healing Wave; [help, target=targettargettarget] Lesser Healing Wave

Alternatively you could have your healer assist the tank:

/assist Tank
/cast [help] Healing Wave; [help, target=targettarget] Healing Wave; [target=tankname] Healing Wave

Pretty much one of each heal is available like this.




I also have specific heals on G-Keys.
My resto shammy can Riptide each party member via G1-G5, which are just obscure keybinds.
Similarly, I can Healing Wave party members via G7-G11, similar keybinds.
I forget exactly which way I set it up, but one set includes alt mods. so its only 5 macro's in wow.
Something like:
/cast [mod:alt, target=ToonA] Riptide; [target=ToonA] Healing Wave
With a keybind like Ctrl Shift F8 through F12 or something similar.