Easy DEs v. hard ASIs
I, too, feel it depends on the individual, barring any FAA memo that mandated a high CFI bust rate.
At ERAU in Prescott, before we had 141 self-examining authority, we would send our students to the three examiners on the field. One was a man who ran a school and 135 operation, and who has since moved to Southern Arizona. The other was an older woman who lived in Chino Valley and who reportedly worked with Amelia Earhart and was one of the woman military ferry pilots of World War II. The third was an old man, whose background I cannot recall. A significantly high percentage of our Riddlers busted with these three individuals.
I would submit that because these three examiners believed that they had cornered the market that had lost, or had refused to exercise, their objectivity regarding Riddlers. In fact, one always whined that our students were always poorly prepared.
Our Chief Flight Instructor had been ordered to reacquire 141 self-examining authority. So, he came up with an idea. He thought, why not send our students not to the three examiners on the field but to other examiners?? So, we did. It was a real stroke of genius. We sent our students to examiners in Phoenix, Scottsdale, Goodyear, Deer Valley, Tucson (that examiner even came to us sometimes to give practicals), and even Lake Havasu. Guess what?? Our pass rate climbed, prodigiously. And, we got our self-examining authority. Nothing had been changed in the training. Same students, same syllabus, same (tough) Riddle stage checks.
This experience proves that despite PTS standards and other objective criteria that even well-prepared applicants can fail, because examiners, for whatever reason, inject subjectivity into their testing. It is wrong, but what can you do?