I unsure how the women in the case of a heter meah rabbonim can be an agunah. A get is held for her to accept by Beis din. The heter is because she does not want to accept the get. Not wanting to accept an available does not make one an agunah, except perhaps by the feminists.
There was an article in one of the chareidi magazines last year (perhaps kolmos) where they described the abuse which goes on. It seems that the abusive heters leave a get, but the get has shailos on it, so she can’t remarry with it.