Difficulty index and discrimination index in questions

If a question is TOO DIFFICULT  for ALL students, then it is as BAD as an EASY question answered by all.  So a question with a difficulty of index   near 0 (easy)  or near 100 (difficult) are exactly the same and have no value in testing. If an easy question is not answered by the top 1/3 of the class, whereas a difficult question was answered by the bottom 1/3 of the class. Then this question has no discrimination index at all. Good questions should have a value of 100, while those with low discrimination index have a value near 0. Perfect question should have a Difficulty Index around 70 for (1 out of 5 questions), 80 for true false questions, and  a Discrimination Index above 30. http://www.washington.edu/oea/pdfs/resources/item_analysis.pdf