We've datamined two new ring runes aimed at healers. These will likely be made available with Season of Discovery Phase 5.
These runes are Rune of Meditation Specialization and Rune of Healing Specialization, and they increase mana regen and healing, respectively.
They are unique-equipped, so you cannot equip two mana regen runes or two healing runes simultaneously. These will likely be available to all healing classes; however, right now, they aren't available to Priests but available to Rogues and Warriors, which is likely a mistake.