These women should either learn the sugyos of tevila b’iyun or not make these halachic determinations. I have come across a few stories (first and second hand) of Mikva Women making terrible halachic mistakes with potentially grave consequences.
I fully agree with your point that women (and men) should be well-versed in halachic areas in which they rule. But the fact remains that we *do* allow women to rule in these areas.
The Wolf