I never said you asked “what the drop rate is supposed to be.” I said you asked “if the drop-rate is what it’s supposed to be.” It’s right there in the title of this thread.
The only way to get Blizzard to check it is to file a bug report, which you said you did. Customer Support and the SFAs are not liaisons with QA and Devs. They can not pass a message on about drop-rates.
Except that most of the time players only hear from others who it hasn’t dropped for yet. If you didn’t have a problem getting it you wouldn’t be on a page that is reporting it isn’t dropping. It only appears to be a 0% drop rate to the players it isn’t dropping for.
There was a mount that some players insisted wasn’t dropping any more but Blizzard confirmed it had dropped in the time-frame mentioned by the poster.