I do not think that the story of Tiresias is that weird.  It is just as weird as any other myths that I have read in the past.  The fact that Tiresias changes from man to woman is not his own doing.  He was changed once he interrupted the snakes mating.  The weirdest part is that simply hitting the snakes with a stick can change someone from a man to woman.  Why?  What, if anything, do the snakes themselves represent?  The gods were so happy that the snakes could no longer mate that they gave Tiresias this great knowledge and power.  I think that a person who can change from a man to a woman and back has more knowledge than anyone.  This person can understand the impossible, something that no real, living person will ever fully understand--the opposite sex.  This is a mystery that as part of human nature plagues us.  Due to love and sexual drives, we are always trying to understand what the opposite sex is thinking, wants, likes, feels, etc.  This knowledge would give a person much power over the opposite sex as well as the satisfaction of knowing, but it would also change their perspective of the other sex and their view of sex itself.  Tiresias's punishment is interesting as well.  It turns out to be more of a blessing than a punishment.  While his actual sight is taken from him, he is given a new sight, an even better one.  He is again given a power and knowledge that no one else has.  He gets the chance to know the impossible, something that people are always wondering about--the future.  This is another mystery that plagues us.  We are always planning, thinking about, and hoping for the future.  Tiresias is lucky.  He gains so much wisdom and knowledge throughout his story.

Narcissus falls in love with himself, or the reflection of himself in the water.  This is a problem because what he is in love with does not actually exist.  It's just an image.  It's nothing.  Once he leaves the water's edge, so does his object of affection.  When he tries to reach for it, he cannot.  Like it says in the text, it is just a fleeting image; it is not real.  This myth tells us that we desire what we are.  People tend to be attracted to themselves, or people like themselves.  They are attracted to others with personality traits similar to their own.  They are also attracted to people who look like them.  Another thing it tells us is that people in general are vain (it's human nature).  People are very concerned with themselves most of the time.  Its like the spotlight effect.  We tend to think other people are watching us more closely/paying more attention to us than they actually are.