They should be correct, since Haavok updated them based on info I emailed him from looking at the dungeon finder levels. Some instances have different level ranges for normal and heroic. We show normal. Maybe that is what you are seeing? Can you give an example?
I think we're close for most of them but there are cases I've noticed where Bliz gives you different level ranges for the same dungeon depending on where you got in (I think Stratholm was one). We only have a single entry for each dungeon so I'm not sure how we'll address this one...