Certainly being directly in the presence of one of the ultimate forces in the universe would make any such effect triggered by a lesser channeler or ter'angreal seem laughable.

Also, I think holding the Power shields you from the effect somewhat because you can see the weave - when you see someone weaving a particular effect and you are prepared for it, you are more likely to associate a strange sensation with being a cause of the weave rather than allow your mind to be lulled by it. Elayne and Nynaeve weren't prepared for such an effect, and Moghedien struck too hard and with too complex a weave for their minds to make the leap necessary to protect them, so they fell under it's manipulation easily.