I for one have always though the Seanchan ads a lot of flavour to the Wheal of Time series. All civilizations in the world of WoT must find a way to handle the stress which the power of male and female channelers places on society, and Robert Jordan seems to have taken great pains to show as many variations on this theme as possible. With channelers on positions of power in all other lands the Seanchan serves an a striking exception. I also thing they serve as an important plot tool in the end. If everyone had conformed to the same values and ethics in the end it would make the future seem a bit boring. All to many fantasy authors feel that they must resolve all conflicts permanently in the last book, but since life does not work that way it is a bit illogical to use it even in books unless you actually kill the darkness in the hearts of men.