ANyway http://web.archive.org/web/200502070406 ... wmob=10440 I trust this website. It says 0.05 droprate. 1 to 1892 chance. Still not 1 to 10k runs. So u need to change it to 0.05 and change rarity to BLUE according to the patch
As Nano stated, investigation was made and drop rate is the right one. Feel free to send report on the Bugtracker after checking that it wasn't already reported (forum isn't the right way to do so).