IIRC, in the Book of Challenges it has a small side bar about playing monsters that are smarter than you. It basically suggests that if the opponents mental abilities are sufficiently high that it has come up with a counter to whatever your players are planning and you should run with that.
Yeah, that does seem to be the solution that most people have suggested; I've tried it many times over the years. I've personally always found that solution very unsatisfactory, though. Just auto-nerfing your players' clever ideas? It doesn't make for a fun game, IMO.