In regards to Callandor and the lack of a buffer, perhaps it is akin to an autistic. Take Rand wielding Callandor. He is ability is immense, "high functioning" if you will. Where a normal channeler can produce a few weaves at a time, he can with callandor create hundreds or more simultaneously. Much like a normal persons can count one at a time or even by say threes or whatever, however a "Rainman" can count hundreds at a time, remember the toothpicks? Now the question as to why Callandor needs a circle with the male not in control? Well it's like Rainman, he can wander about with his high functioning ability, raging when things aren't to his liking (picture rainman hiting his own head). Until His brother finds him and uses his ability to count cards. All of a sudden this crazy power is harnessed and focused into an unstoppable force. So it is with the wielder of Callandor. In fact the more I think about it the more I can see how autistic Rand and the other Asha'man are :p