The issues with psychopaths in the workplace is that they're very good at finding high-ranking patrons to protect them:

What interested Babiak most about this case was the fact that while those closest to him were convinced of Dave's manipulations, irresponsibility, and lack of integrity, those higher up in the organization had been convinced--by Dave--of his management talent and potential.

-- Robert Hare, Without Conscience Ch. 8

By the time someone complains about the psychopath, upper management has already gotten an earful about how awful the psychopath's coworkers are and how badly they stifle his ability to shine. Psychopaths are good manipulators. Hare mentions how even he, one of the foremost experts on psychopathy, still gets taken in by them.

First you imply that the "actual frequency" is a feature of the territory -- I'm not sure about that at all (the underlying "feature" is likely to be a continuum with a semi-arbitrary threshold imposed by a map).

This is correct. The Psychopathy Checklist does have an arbitrary cutoff point.