I've seen some JWs do okay working for other JWs, and I've seen some JWs become awful employees.
The typical excuse for the terrible JW employees is, "they're still just imperfect humans."
That completely crushes the idea of there being any "spiritual paradise" or "da troof changes lives". Fact is, the good JWs would still be good people even if they weren't JWs, and the bad JWs are completely unaffected by "holy spirit" or magical "new personalities."