Well there is that. However, I think it's a strength thing too. In my opinion you have to be able to destroy another channeler's conduit to the Source. Therefore I don't think someone like Moiraine could still another channeler, unless that channeler was Morgase or Sorilea, and maybe not even then. Very strong channelers like Egwene and Nynaeve can make razor sharp shields backed up with a lot of saidar, so that when they hit you they just rip into your connection to the Source, and leave you ruined forever.



Once again I think it's a strength thing. Nynaeve makes a razor sharp shield instantly and sends it Moghedien's way. Egwene needs to prepare the shield, which is a time-consuming process as she describes it, taking at least a few seconds. Rand, on the other hand, is so strong that he doesn't even need a sharp shield. He just sends fists of Spirit, and tramples on the other channeler like an elephant. He probably couldn't do that to someone like Lanfear, where he would need to prepare a good shield like Egwene and Nynaeve did, but for a woman as weak as an Aes Sedai, they're road kill for him.