It seems to me that despite your track record in the past, the Dark One cares more about what happens with the Dragon when you interact with him. You can hardly call Semirhage a failure - she seemed to be one of the Dark One's favorites, and of all of them, her defeat was the least spectacular. It was almost impressive that she stood her ground and it really seemed that even with her scene in TGS, she did well for herself. Taking the Dragon into account, Ishamael has been a spectacular failure since day one, and only seems able to influence background plots.

It just seems to me, and other readers have commented on this as well, that RJ assigns the worst punishments for female villains as if they are supposed to possess the superior judgment, whereas the males seem to get off with a shrug or die pretty cleanly.