A sub-bullet for In Spite Ofa Nail reads "Despite all this, and Dragons being at least an order of magnitude more intelligent than humans, and apparently breeding very quickly, they haven't taken over the world."

Do we have any evidence in the books that dragon intelligence is that high? To be sure, most dragons are very smart and many have an aptitude for math that would qualify themselves as mathematical geniuses, but a full order of magnitude would be god-like intelligence.

I'd say that typical dragon intelligence is at the high end of the human-norm bell curve.