^ this.Quote from Angzt
That wasn't a change. It was just a confirmation of what the drop rates have always been.
Whether these drop chances apply to Bosses is unknown, they might just apply to SuperUniques, as you mentioned yourself.
Also, the odds of not getting a drop in 20 runs with a 14.9% drop chance are just under 4% [(1-0.149)^20]. Low, for sure, but not low enough to indicate a bug, it might really just be bad luck.
I'd say just wait it out until the new rates are in:http://eu.battle.net/d3/en/forum/topic/10219142187?page=6#103