I was actually put on the Harassment investigator's course years ago (in the early 2000's) (as part of an ambitious plan, the investigators being trained at 31 CBGHQ were "paired" with similar trainees from 32 CBGHQ so if a case came up in 32 Bde, we would go to Toronto, while if a case came up in 31 Bde, they would come to London, to avoid any charges of bias).
Shortly thereafter, the investigation of harassment cases was turned over to civilians. AFAIK, there are no longer any training courses for HI's in the military. Indeed, it has been years since I have even heard about Harassment Advisor or Workplace Relations Advisor training, although I have no reason to believe these roles have been eliminated.
As to the "why's" of this, I will leave it to others who are better versed in the subject.