I wrote:
Tonight I'm going to temporarily dyke the header out of one of the Reference Desks and see how quickly it refreshes then.
I performed several different tests, with crystal-clear and consistent results: the problematic transcluded RD header results in edit or first-view times of 60 seconds or more, while removing it reduces the time to approximately 10 seconds.
See [[Wikipedia talk:Reference desk#Houston, we have a problem.]] for more information.