Yeah, we all know that Oculus kinda sucks, but now we've got some numbers on it -- or, more accurately, Flyv does. One of my feral Druid colleagues has been examining Armory data on completion rates of Wrath heroics (and incidentally took a peek at how long it takes for the average person to go from dinging 80 to a full Naxx clear). The numbers aren't too surprising: heroics that correspond to the earliest Wrath "regular" dungeons -- Violet Hold, Utgarde Keep, and the Nexus -- are far and away the most-completed heroics. Oculus -- and to a lesser extent, Ahn'kahet and Halls of Stone -- languish at 40, 51, and 58% completion rates respectively.
Halls of Stone surprises me somewhat, as I really didn't think it was a difficult heroic (outside of running a Druid tank on the Brann Bronzebeard event), but Ahn'kahet is universally cited amongst tanks and healers for LOS issues and nasty damage. And Oculus...well, we've talked about Oculus here before. I still think the concept of the dungeon itself is fantastic, but the moment that one or two embarrassed people in your group admit that it's their first time on the drakes, you know you're in for a long and ugly run.
I hope Flyv revisits this data at some point, because I'd love to see how the numbers change over the course of Wrath. With achievements introduced only as BC was ending, we don't really have a good look at how dungeon popularity and completion rates evolved there, and I think the numbers say a lot about the content players prioritize when they get a toon (or multiple toons) to the level cap.