I would consider changing the Holy Priest to a Disc Priest.
Disc does have its issues, but Disc > Holy from a DPS point of view.
And Smite spam, will passively heal whoever is lowest within a medium range of your kill target.
You get much stronger PW: Shields, and then Pain Suppression, Power Infustion, Divine Aegis etc.
You still have the Druid healer for excellent AoE healing and both are very mobile healers.

I'm not a fan of Hunters, at least boxed.
But if you're willing to deal with auto-switch to melee at close range, which breaks follow... on a class that otherwise plays like a caster..
It is your team, and Hunters bring decent DPS and Utility.