I been toying with this idea for a bit and since WoW has been borrowing inspiration from other games for the longest time, why not throw a warcraft themed spin on the old Red Mage from FFXIV
3rd Spec : Exorcism
Main Stat : Intellect
Role : Caster Melee
The spec would fill up two bars by casting from 2 schools of magic : Shadow and Chaos. They would have an ability where every 2nd spell they cast would be instant. They would want to keep the Shadow and Chaos magic bars around the same as if they fill one up too fast, the other fills up slower. They would have melee abilities that could combo into one another, however they do not hit hard, unless both magic bars are filled up, then they become empowered and hit alot harder.
They would attack from ranged, casting different Chaos and Shadow magic spells, with empowered spells drawing power from Void and Fel respectively and even some Arcane. Once they filled up the two bars with abilities, they would fel rush in, perform their melee combo, then vengeful retreat back to ranged.
Their demon form would involve them throwing their warglaives to the ground and causing a Chaos and Shadow elemental pet to spawn and attack the target while the demon hunter is hovering in the air flapping his wings, and able to cast while moving. The spells would all be stronger and hitting harder as well.
This idea draws inspiration from the gameplay of the Red Mage from Final Fantasy XIV and the lore and Aesthetic of the Illidan encounter on top of Black Temple.