Keep in mind that none of the Forsaken who appeared at the Cleansing would have willingly gone if they had not been ordered to do so. It was almost suicidal given the amount of Power being channeled and the very real possibility that there were were more channelers in the Circle wielding the Choedan Kal and an attack from any one of them would be much too swift and powerful for any single Forsaken to counter.

Rand really wanted to get this done as soon as possible, and he also had trust issues, so he limited the amount of people performing the task to him and Nynaeve.

If the story had gone differently and he was able to trust all of the channelers among his friends and/or had arranged the task and defense differently, this could have been a major disaster for the Dark One.