I really would like to see a Holy/Disc DPS spec.
I mean, you have everything else, so why not? There's evil shadow caster DPS in Shadowpriests and Warlocks. Elemental DPS in shamans and mages(they utilize fire, ice, and even arcane). You even have paladins, who utilize holy spells combined with melee attacks.
But no PURE holy caster class in the game? Really?
I enjoy the mechanics of Smite and Holy Fire. I also enjoy Discipline's DPS qualities of power word: Shield, and am just ashamed that it has been nerfed in recent times.
Obviously, what would the difference between Holy DPS and every other kind of DPS? Shadow-type DPS specialize in DoTs. Elementals focus heavily on big crits and proccing.
So Holy should focus on something entirely different. When I come up with what, I'll come back to this post and share my ideas