I highly suggest you watch this video clip on the matter: https://youtu.be/4vebn1AN6KY?t=618
I don't get the OP, are you asking for the healer you choose to be better at healing than the two other healers ?
In Panthon, the three healers are designed to be as good as the others in that specific task, if a Shaman or Druid out heals you it might mean you're not playing at your fullest and the problem would be... you.