I think you can only get mindreading up to 15 in the flames of vengeance expansion. Otherwise it's locked at 10. Or 13. Or something like that.
Basic rule of thumb for mindreading is: If it costs a LOT to mindread, then they probably give you something good for doing so. Maybe you'll trigger a hidden treasure or something.
But yeah, the only time you'll really want level 15 mindreading is in FoV when everything costs you like 25k XP to mindread.
