I am about as far from Charedi as possible, but Avi Weiss is not a Talmud Chacham. Maybe he has other postive traits that are needed in the community, Certainly he draws people who would not go to any other stream of Orhtodoxy. The people he draws certainly are not becoming Satmar anytime soon or moving to Lakewood.
However that still doesnt make him a Talmid Chacham or a Halachic Authority.