I read another post of a boxer who was going 5x Resto Druids.
And then using Magma totems for AoE, as they just healed each other.
This I believe was for Arena against cleave type teams.

I have 5x Discipline Priests at 60th from RAF.
Haven't leveled them since, but thought they'd be a change of pace in AV's, healing from the back.
Pain Suppression on round robin etc.

My 5x Boomkin team is fun.
Even though they're not Resto, 5x Rejuvenation and 5x Regrowth on a toon makes them almost immune to damage.
Down the road with 5x Lifebloom's ticking away as well, will be even more sickeningly fun.

Disc Priests can Mind Flay, Mind Blast, SW: Pain, Devouring Plague, Holy Fire and Smite.
Resto Shammies can Flame Shock, Lava Burst, Chain Lightning, Purge etc.
Resto Druids cannot use their Balance spells in Tree form, which is a major strength of the spec.

Still as far as keeping one person alive, it would be very strong.
I'd personally lean towards a healer spec that has some dps options too.