Well, you know I’m Elemental. I can throw lightning.
Our last Karazhan raid I tied for 3rd in Damage Output.

But I was a healer once.
No record of it, like for the Karazhan raid, but last night 5 of us, 1 person brand new to the Caverns of Time, went to Durnholde Keep and the Black Morass. I was the only healer. The Warlocks can life tap, and the Warrior is so geared he takes relatively no damage. No deaths.
Elemental Shamans *CAN* heal. Just give it a try and be prepared with water, mana potions, and get yourself some good healer add-ons like Healbot and Clique and Grid. (I kept Thrall healed via the Focus Frame.) You can do it.

This is a lot of the non-set Shaman healing “set” found in normals and heroics. (The +88 Healing Chestarmor was from a quest in Nethestorm.) I’ve got nearly +1000 Healing in it. Just a few gems different and this would get me started in Karazhan as a Restoration Shaman healing.
But, for now, I’ll remain the Elementalist that can heal.