Well, I am not an expert either, but I do have a dyslexic child, and I have never, ever heard of making a dyslexia diagnosis based only on a WISC. I believe that is not standard at all, and doubt it could be done. In fact, many claim that dyslexia does not affect IQ scores. A dx of dyslexia is usually made after an extensive battery of tests -- my son was tested over five afternoons, and was given tests of reading and phonemic awareness in addition to IQ.