Perhaps if you spent a minute thinking of the question instead of how to best make yourself sound more intelligent you would realize that Shadow prophesy and corrupted Light prophesy are very different things. The Seanchan are clearly working off the same general Prophesies of the Dragon with certain key elements changed. NOT Shadow prophesy. No one is questioning the veracity of the Shadow prophesy. The question is which Light Prophesy has been altered in order to make for conflict.

The Seanchan are designed to be a repulsive society. Slavery and an oppressive caste system are hardly meant to engender warm and fuzzy feelings. Unless of course you are a sociopath.

It may be that there are damane with greater control of the Foretelling Talent ... We've seen at least one who seems to be able to call them up on demand ... But that is NOT the same as the Omens that Tuon and Selucia follow ... These seem more like folklore on the surface, counting ants, owls hooting and such ... But could well be more akin to what the Two Rivers Wisdoms do to fake the ability to Listen to the Wind. These are not in any way linked to the Power, but may have legitimate sill ... Even though we know when something doesn't happen according to the Omen people assume the individual read it wrong. Tuon says as much when she says "Selucia must have counted the ants wrong".