Do you think Varys knows anything about the threat in the North? Wouldn’t he have at least an informant at the wall to send word if something of importance happens? Tywin bothered enough about the Night’s Watch to try to influence the vote of the LC to set a Lannister lackey in place. The Wall might not be top priority even in the eyes of Northernes at the moment, but would Varys not at least keep basic tabs on what’s going on?