Everyone has their own way of doing things. I kinda like only 1 heal button. I also HATE targeting anything, so I put the in the options who should get the casts.
I like to heal whoever is getting beatten on. For my hunters (5 hunters and 5 pets), I can put GotN on whoever is taking the most damage, without using 10 buttons. For my locks (4 locks, 4 pets, 1 spriest), I can heal whoever is "tanking" at the moment with 1 button. No thinking, no worries, just heals. It also works for me to heal whoever is getting beat on in BG's. You wouldn't want 35 buttons to heal other people.

/castsequence [@focus-target-target] reset=target/combat/12 TinyHeal, SmallHeal, BigHeal, OMGHeal
I focus my main, then whoever is getting beatten on by the mob my main is targeting gets healed slowly, then bigger. So if I just need tiny heals, I press it once, if I need more, press it more.
You can add in the same macro to do different things.

/cast [@TankChar, nocombat] Earth Shield
/castsequence [@focus-target, help] reset=target/combat/12 Lesser Healing Wave, Lesser Healing Wave, Healing Wave
/castsequence [@focus-target-target] reset=target/combat/12 Lesser Healing Wave, Lesser Healing Wave, Healing Wave

If out of combat (right before a pull), you can put earthshield on your "tank". You can heal whoever your main is targeting (in case of a specific person getting hurt even if no one is beating on it). You can heal whoever is getting beaten on. All in one button, no thinking, nothing.

One nice thing about shammies is healing stream totems stack, so you can most times just put down mostly healing and 1 mana (mana doesn't stack) and you won't need much more than a lesser healing every so often. You can also stagger your heals from people so you can get less or more from everyone or just your resto. So if you LHW from 2 people instead of 1, you get a stronger heal, but share the workload over people.

Char 1:
/castsequence [@focus-target-target] reset=target Lesser Healing Wave, , , ,
Char 2:
/castsequence [@focus-target-target] reset=target , Lesser Healing Wave, , ,
Char 3:
/castsequence [@focus-target-target] reset=target Lesser Healing Wave, , , ,
Char 4:
/castsequence [@focus-target-target] reset=target , Lesser Healing Wave, , ,

Just my 2 copper.