If the test turns out to be a massacre, the faculty may elect to reduce the percentages needed to pass. Examples of this include the Fall '90 and Spring '92 exams. I do not know of anyone who has taken the DWE four times. When a subject becomes totally obsolete we make it a required course. When asked to name the core class they fear the most, most DWE takers will probably name 151.
Error analysis is a commonly included topic.
Almost everyone else couldn't either. In 1978, the famous tightrope walker Karl Wallenda fell 75 feet to his death. For some reason, he became obsessed with the fear that he might fall. It was the first time he'd ever thought about that, and it seemed to me that he put all his energies into not falling rather than walking the tightrope. The ones who are able to perform in the clutch, when the stress is greatest, are the ones able to focus their minds on the tasks needed to succeed, rather than thinking about the risks of failure.