Experience pops aren't informed nor visible by that green arrow that indicates an increase, so they are easy to miss. I did get an experience pop last season as did several posters here, so everything's working. Your ordering of scrimmages, league, tournament, BBB is generally correct in order of which gives more experience, though the difference is minute (Except for scrimmages which gives much less experience) and affected by other factors.
Solid data on how experience affects a players performance is hard to come by, especially you would require players with the same skill set, GS and varying levels of experience to see it. Charles I believe posted on the forums that experience helps in decision making on whether a shot is good enough to take or to pass the ball and look for another opening. An inexperienced player might be more susceptible to taking shots when the chances of making it is poor, better experienced players are better equipped to judge which shots are good and when to pass.