It would have been a state of open war for the first part of the offensive, and the characters we know as leaders (Egwene and Elayne) were most likely returning to their nations after Tarmon Gaidon right as the Seanchan were striking. It's not too hard to believe that Egwene and Elayne as stronger Aes Sedai, would have died in the fighting either early on or within a few decades. I doubt Nynaeve would have left either to face their battlefields alone, and I think she would have fallen, too. Aviendha probably died when the Aiel were first being targeted.

It would be even sadder if they were to have been collared because I consider that to be a fate worse than death, and this could be why they weren't mentioned - those characters were broken by the a'dam and can no longer be considered to be the same people they used to be.