Take this with a grain of salt... I've not taken my team into heroics yet.

I was running 5x Elemental Shamans, but have switched to 1x Prot Paladin + 4x Elemental Shamans.
One of my shammies has dual spec. I believe they are/will be 54/17/0 and 0/15/56, they're mid 70's so half a dozen points short each.

For questing and such, I just go with 4x Elemental and 1x Prot and blow stuff up.
Play the prot as the main, and the elementals as the slaves who assist party leader.
Have considered moving to the "target=targettarget" system, but haven't yet.

For more challenging content the one shammy goes Resto, which gives me Prot Tank, Resto Healer and 3x Elemental DPS.
Since mana totems don't stack, and the resto's mana totems are superior this toon always drops the Mana Spring.
Even as Elemental, for simplicity this shammy is the one that drops the mana totem.
The Elementals drop either 3x Healing or 1x Healing and 2x Cleansing depending on the situation.

I drop a lot of Grounding Totems. All of the shammies have the talent to knock 2 seconds off of the re-use time.
In theory, I'm negating a ranged spell every 2 seconds, but non-targeted AoE's like Flamestrike or Blizzard are not absorbed.

The Paladin is exceptional at holding threat against melee range opponents.

All of my Elemental Shammies have their dps set up, to attack the paladin's target and either cast offensive if the target is [harm] or healing if the target is [help].
Chain Heal assists party 1, so whatever my current leader (almost always Paladin) is targeting is the target of chain heal.
The syntax I use is:

#show Chain Heal
/assist [target=party1target]
/cast [help] Chain Heal; [help, target=targettarget] Chain Heal; [target=party1] Chain Heal

So if my Paladin is targeting a friendly, then the first condition is true and every shammy Chain Heals the target of my paladin.
If that target is hostile then the second condition comes into effect - is the target of the paladin's target friendly? If yes, they're the recipient.
Honestly, this second condition applies the most, because when my Paladin is killing something its almost always attacking the pally or a shammy.
The last condition defaults to heal the current leader.
I use a Party Leader system, where the current active toon is Party1 (group leader).

Resto shammy has the same Lesser Healing / Lightning Bolt macro as the Elemental Shammies.
However, her LB, Flame Shock, LvB and Chain Lightnings only fire off with modifier keys, so they don't conflict with her heals.
I have Healing Word and Riptide on G15 keys, specifically able to heal Party 1 through Party 5, now that party order is fixed according to invite order.
I also have a Healing Word macro which targets the same as the above Chain Heal macro.

I've not done heroics with this team configuration.
However running 4 druids and using this syntax with Rejuvenation, Regrowth and Lifebloom.. they're pretty impervious to damage.
As far as AoE healing, a resto has Healing Stream Totem and Chain Heal - which as far as raid heals go, is very effective.