Constant AE has a use because it's always up when you need it. CD AEs tend to do enough damage that you might reasonably want to use them in single target, even if your rotation is pretty full (a good example is Wake of Ashes). But we already have Wake of Ashes, so it seems like overlap to have another CD AE.
There are other benefits to Consecration too. If you look at Prot, they have all sorts of cool tools that go along with it. They have one that makes it Snare and heal (and by extend triggers Purity in PvP, to remove poisons/diseases), and another that makes it remove movement impairments when activated. It's just a cool mechanic and Prot seems to have the monopoly on that. I don't so much mind I guess, but it's crappy that we just get a watered down version.
Anyway, I think we need on demand AE regardless. Something that you probably wouldn't use unless there's a bunch of targets and can have ready to go any time. Consecration could reasonably fit that bill, but at present in its talent, it doesn't do that.