My theory on how Rand will cleanse the Taint:

         I believe that Rand will cleanse the taint before Tarmon Gaidon.  I believe that he will do so by linking with a group of people while using both of the Super Sa'Angreal.  There should be two circles.  One to cleanse the taint, and one to keep the flow of Saidin both coming and to keep the Dark One at bay.  He can not just use the 7 seals for a focus point since they are weak as clumps of dirt.  I feel he must construct a self tightening web around the bore, and Shayol Ghul, to keep the Dark One away.  Also he must do this so that in the return of the Age of Legends someone can bore through it again.

        The circles should consist of on one side, Nynaeve, Logain, and Flinn, andEgwene, and  on the other circle there should be Rand, Elayne, A vienda, and Hopefully Moiraine… although that is a big MAYBE.