We've seen her do it, and he confirms that if he hadn't done something about it her weave would have settled on him.

To actually overwhelm Rand would take about 3 women of Forsaken strength. At those levels he would be able to do nothing. It would be Cyndane vs Alivia except that Alivia is very skilled - like Fionwe said. Lanfear wanted to link with two other Forsaken to assure their victory if they trapped him, so this confirms what he said. However, if one Forsaken brings him to his knees like Lanfear did, there is an opening for a shield.