It was previously reported that "Sanderson said that we had seen Mesaana's alter-ego on screen as of Knife of Dreams, but that we had not seen Demandred's alter-ego on screen as of Knife of Dreams. Sanderson would not elaborate on whether Demandred's alter-ego had been seen in The Gathering Storm — Sanderson didn't want to narrow down the suspects for us if Demandred really had appeared in The Gathering Storm."
Galgan was seen in KoD.

It also doesn't really fit with Demandred's comments in TGS, prologue, that his rule is secure, or that he gathers for war, since Fortuona rules the Seanchan.

Also SH's comment to Semirhage in TGS that she lost valuable pawns makes no real sense if Demandred would still control the Seanchan (and it's in itself unlikely that there were two Forsaken among the Seanchan).