Semirhage wasn't equal to cracking the safe, Elza brought her the Domination Band. Someone else cracked it. They would only have to be roughly equal to Cadsuane (very roughly) and/or skilled with reading and reversing weaves. We don't see a lot of ingenuity in that department from the AS; too set in their ways. That's more of a Wise One thing... but I still find it so hard to believe that any of Rand's WO's is a Darkfriend.