Just my thoughts. Everyone might do it differently, find a way that works for you.
I never like doing /tar for pretty much anything. I use options in the casts. I focus my main, then I use:
/cast [@focus-target, help] HealSpell
/cast [@focus-target-target] HealSpell

The first one heals whoever your main has targeted (for friendlies or for emergencies). The second one heals whoever the mob that the main is targeting is beating on. So pretty much heals whoever has aggro. These don't require anyone to be in your group and works no matter if in a group even (different raids in WG and such).

Other people make a heal for each player (so 5 buttons), mine is 1 button. Easier for me to remember. They also might put in names in the macros, but I use the same macros for any group, so I don't like changing them. You can't really do just /party1 or /raid2 and such, since the group's position will probably change.

Since druids, I might make 2-5 different kinds or heals. (using shorthand for spells)
castsequence of norma damage (/castsequence [@focus-target-target] reset=target/6 Rejuv, Lifebloom, Nourish, Regrowth)
It heals in increasing amounts, if you don't need that much, just don't press it for a little and it will reset.

Big heals with sustained damage (/castsequence [@focus-target-target] reset=6 Rejuv, Lifebloom, Lifebloom, Lifebloom, Nourish, Nourish, Regrowth, Nourish, Nourish)
It gets a HOT on them, and then puts 3 rolling Lifeblooms which get refreshed by Nourish, adds in a bigger regrowth for umph and then refreshes them all again.

Spot heal 3-10 people. Doesn't rely on them to have aggro or a person to be beating on them, hence, help
/castsequence [@focus-target, help] reset=target/4 Rejuv, Lifebloom, Nourish
Mash 2 times for a little, 3 times for a bigger, but mostly used to to get more people than super heal one person.

AOE healing. Would need to use round-robin to make it more effective. You can pick any modifier you want, or just take it out and only put Wild Growth in there
one druid at a time: /cast [nomod:CTRL] Wild Growth; [mod:CTRL] Tranquility

Again, everyone has their own style. Just pick one that works for you and run with it, might even mix a few together. Good luck.