Aran'gar specifically stated its tastes had expanded as part of accommodating the change in gender. In other words, still attracted to women, but now interested in men as well. As for Rahvin, his sexuality is so obviously tied to his self-esteem, it's pretty obvious that he'd have had obvious male partners in his stable. If anything, he'd be even more desperate to make sure the males were devoted to him than the women, given the WoT perspective on gender differences. I wonder how much Graendal really was into sex, and how much was just about shock value. She probably did it a whole lot with anything with a pulse, because she isn't one to do things by halves, but I wouldn't be surprised if that was a deliberate choice to check off every box she could think of, instead of true indulgence in repressed desires. She and Semirhage seem kind of asexual to me, insomuch as they get their rocks off with more abstract appetites.