As a standard action? I see no reason why it shouldn't be at-will basically. Now, there are of course some feats and paragon paths, etc that modify it. Once it gives you a free basic attack (so it's at least comparable to a standard action) and giving combat advantage to everyone, etc ...it becomes something people might actually use, and not necessarily something that should be at-will.
So make the 'enhanced' versions work just 1/enc.
Bluff-for-CA being 1/enc has always kind of irked me. It just sort of stands out in a weird way.