Prayer is 'never' a waste of time if it makes you feel good for doing it.  Those who get together in prayer gatherings have the benefit of group therapy and  self satisfaction of good will.  The waste of time is the expectation for an outcome.  There is none.  It is like picking up the phone and speaking with no one on the other end.  So what then is the "unbelievable" the expectation of an answer or that some of us have realized that it has never happened.