That could work. Vanguard: Saga of Heroes had a Healer class called Blood Mage. It had some interesting techniques. If I remember right they were a bit similar to Discipline Priests in a way, gather Blood away from the enemy to heal their targets.
Personally, I would call it a “Flesh” spec for a reason I’ll get to in a minute.
Honestly, I don’t like it because it has too much power. I’d rather they be closer to the Necromancers of Warcraft 3, summoning skeletons for a short period. Offensively, they’d be akin to Dark Age of Camelot’s Theurgist who use temporary pets (20s-30s life span) for their damage.
It would be a Cloth-wearing DPS/Healer class. One of the DPS specs would be Bone, and focus on numerous summoning abilities. The other would be Flesh and focus on Hots and Bone Armor-style ablative abilities.
It would be interesting to borrow an old skill of Death Knights when they could resurrect players as zombies. Adding this as a kind of way to do for other players the way Holy Priests can forestall their defeat as an angel could be interesting as well.
Aside from the Necromancer concept above, Wardens could be interesting. Make them a Mail-wearing class and provide stealth DPS and Tank specs. It’s a little lower in priority for me because we already have so many of those right now (though Mail could use more representation).