Ive been thinking of 5x enhancement shaman with some modifications from "optimal" dps for increased survability:

mwx5 goes to healing rain x 5 instead of lightning bolt. sub resto instead of elemental to get the +healing/healing received talent and get the shock talent which will buff your healing rain ability (i.e. cast a shock every 10s and then follow it up with healing rain to get the improved healing).

Dont know if it would be enough healing without a tank since youd obviously be in melee.