Balance and Feral have massive synergies between their perks, passives, and talents around Healing Touch - which is what is giving them like ~70k heals. Windwalkers are pretty much the same as MoP - nothing nerfed.
Ele and Enhance Healing Surge isn't too impressive, even with +100% effectiveness on themselves. Shadow Flash Heal isn't worth the combat GCDs, while Devouring Plague self-healing is nerfed compared to Live. Ret heals are in the right spot right now - but they definitely don't need to be nerfed.