Because of the pseudonyms, they cannot bias the grades for or against any student. The professors who grade a question are usually different from the ones who wrote the question. Each question is worth up to 45 points. When finished, the professors compare the marks they gave to each student. Finally, the results are tallied and the professors discuss the results during a Faculty Lunch.
Results vary considerably from year to year.
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.