Well shamen don't have that many aggro drop options besides dying and using their ankh lol, but having mail heal gear, however little there is of it that is pure heal, would give them the armor to take another hit or two so the tank has time to grab it back off

And I'd forgotten about the priest-specific heals like their AoE heals and Prayer of Mending...oh my god Prayer of Mending is an absolute god-send and healgasm, best fucking heal ever introduced, my guild leader dwarf priest has saved my ass with it so many times as a boomkin offtank in heroics and raids lol