I just barely played a game as IG against an SM player who was clearly tech rushing and couldn't defend against my four thirteen member squads with grenade launcher "rush" with nothing but infiltrated plasma scouts. Everything was going well until the librarian popped out and one smite killed about thirty guardsmen. Oops.
Now that smite is incredibly powerful, what can the IG do as a defense? It's late and I forgot to save the replay, but any advice would still be appreciated.