So this is a sleep deprived Kel, having a mind working when I am not. Go go procrastination!
...
Anyways! Holy Nova kind of got relegated back to its pseudo-useless place in the spellbook, where hurray it's an instant spell, and if you're lucky you might be able to use it to hopefully pretend to destealth a Rogue. This spell shone with the use of a certain Glyph in Ulduar and Trial of the Grand Crusade, two fights in particular, and then once more for Arthas heroic, but hasn't really seen any value since then despite being revamped to no longer be party-limited.
What can we do to make this spell work, for even one spec? Incorporate it into Discipline's hybrid damage/healing concept, with a couple twists. Divine Accuracy would have to be changed to "your holy spells", including Penance, Holy Word: Chastise, and Holy Nova.
Train of Thought would increase the radius of the heal of your next Holy Nova, if your last Holy Nova did damage (lasting 6 seconds).
Evangelism's damage bonus would apply but not trigger Evangelism (just as it does through Penance). For the record, it should also do the same for Holy Word: Chastise.
But more importantly, the damage done through Holy Nova would trigger a single Atonement, in addition to its multi-target spread healing.
You want bigger numbers, knowing exactly where they land? You'd pick Prayer of Healing, with its guaranteed Aegis. This is just adding to Discipline's multi-target tools, giving it something "fresh" to play with its niche role that it carved out for itself. Would it be good in all situations? No. Is Atonement good as a single target heal in all situations? No, you still use Greater, Penance, etc. Having Holy Nova as a tool that you could use under these circumstances wouldn't be a "be all-end all" by any means necessary, but it'd put the spell on some Priest's bars, no?
As my usual close goes: "What's your take"?