Yes, I think you were being unrealistic to expect omnis to excel at that holographic soundstage that I've heard with the best recordings. Again, this is just theory, but here's why:
Soundstage is an illusion. The speakers are not only recreating the direct sound of the original recording hall, but also the reflections. The better speakers are at recreating those sounds, the more "you are there" you will get. Omnis are going to add their own (well, the room's) reflections, because they're literally projecting sound around the room in a more energetic manner than regular dynamic speakers, which tend to beam somewhat.
At least, that's my story, and I'm sticking to it. I read a review recently of the smaller MBL in which the reviewer claimed excellent imaging, but I tell you what -- I remain skeptical.