Found another solution to Mindbender + Mindsight wrecking the game.
Telepathy Block from BoED (Brd 5, Clr 5, Sor/Wiz 5) only lasts 1 round per level, but it is an 80-foot radius emanation, and a Widened version (8th level slot) shuts it down completely. Although it comes from the BoED, it isn't a [good] or exalted or sanctified spell, so as far as I know, there's no reason the bad guys can't use it too.
This just adds to the gem of Hellbreaker, which can also shut down Mindblank, in a limited fashion.
Granted, it would have to be used by foes that know what to expect, so it wouldn't come into play in a lot of situations.