I think RJ's typical way of writing is that the the future victim themselves think or say something that figures into their defeat. Semirhage, for example, thought that she would not allow herself to be sacrificed and the Dark One enabled Rand to access the True Power to destroy her without blocking Rand's access to it, which could have been done. Ishamael thought that Rand was an untrained farmboy that could be scared into obedience, and he ended up being destroyed because of his own ignorance as to what Rand values. So, to me, Aran'gar's statement has nothing to do with any of the other Forsaken, and may have more to do with his impending defeat.