this is my theory, to cleanse saidin think back to the EoTW. the eye itself is a pure version of saidin made by male and female aes sedai during the madness. Moiraine said that they killed themselves in the process but it was necessary. With this new male bonding thing as a possible buffer against the taint, i believe that rand and nynaeve together with the male and female sa'angreals can cleanse the taint without anyone dying. a possible circle or such to give more power is possible. I do have to agree that the seals have something to do with the taint and i'm working on a theory about them as well.(possible channeling all of the power into the seals to cleanse the taint as apposed to destroying them)