They have such an ability: http://www.wowhead.com/spell=30283
Just because I was too lazy to look up the correct spell doesn't mean it's not accurate for comparison purposes.
Though it doesn't do any damage any more like it used to.
Mechanically speaking, a "Nova" spell radiates out of the caster. Fire Nova (totem) radiates out from its Totem. Frost Nova radiates out from the Mage. Holy Nova radiates out from a Priest. Shadow Nova radiates out of certain bosses (Such as the Halfus you linked.
Shadowfury is not a nova spell, it is targeted on the ground. It also doesn't deal damage, and Holy Nova doesn't stun. It is in no way analogous to Holy Nova.
GC said that they want disc to have another AoE healing spell to match all other healers, maybe then they can nerf Atonement even more without making it useless or overpowered, but he went on to say that it would be something addressed in a future expansion. I'm still holding out hope that it would be Holy Nova, even if they didn't make it targeted, I loved the spell and it is a damage/healing spell, which fits with our playstyle.