At any rate, I'm not saying there's a problem since the miners have only been online 3 weeks. I just haven't seen anyone else post a detailed comparison of actual vs. theoretical returns.
Unless you have problems with miners, it's just bad luck.
You did 14 blocks with average rate of success of 19.68 (if you correctly calculated it). Poisson distribution gives 11.8% probability of getting 14 blocks or less with average success rate of 19.68. http://stattrek.com/Tables/Poisson.aspx
One every 9 persons was as unlucky as you. Those who are lucky and get more than average do not post on the Forum.
If you want less variability, use a pool.