15 runs is not a very big number to draw any conclusion, that's not even the beginning of a small number. Statistic needs a HUGE amount of tests.
And on the overall, when you start to get severall :SR: weapons on raids run and additional accessories on a regular basis, you start to believe in the eidolons. I have no numbers nor anything else as proof, and they could have introduced a bug, why not. But still 15 run is not enough to demonstrate anything.