Fyr'Alath Drop Rate/Issue

I was advised to open a bug report by support on this. I am trying to determine the actual drop percentage of this item via the BLP system. On my pally (Machiina), I have a total of 16 heroic kills. Based on the loot percentages based on number of kills via the below article, the BLP should kick in and make it a guaranteed drop on the 15th kill:

I am trying to understand what the actual drop percentage is with the BLP, if the article referenced above is incorrect. Most of the online articles regarding the drop rate seem to support that this should be a guaranteed drop after 15 kills as well, but that is not the case for me. For reference, my last kill (16th) dropped another Greater Ember, which has been the case for every run to date. Any input or assistance would be appreciated. Thanks