WoW, best PVP healers?

I was looking at some stuff, and doing some research and although im a priest, I realised that if other cles (druids, palladins, shamans) could also heal, which one does it best for pvp? I mean, priests are best known for our healing, but if 3 other cles can do it too, we are just obsolete. I understand that priests are also good at dealing damage, but cmon, we all know that priests are mostly used for healing. But that means you could just be like, nah we dont need a priest we can just get a druid to heal and fight. Which is best for pvp?