Just an observation.
It seems the majority of people are assuming that the shadow in the warp will just bugger over the Astronomican the moment the nids get close. But no one seems to have considered the alternative, that getting right up close to a psychic beacon powerful enough to cover most of the galaxy could actually fuck with the nids and the hivemind instead.
The human appendix. Proof of a higher power. A divine kill switch so to speak.
No one really likes a smartass, but people tend to like a dumbass even less.