RNG is RNG is RNG.
I farmed Baron Geddon for his Bindings, for 6 years.
I got Attuman's and Onyxia's mount in the same evening.
RNG is RNG is RNG is RNG.
I Fished for one of my last pagle fishes, got the Sea Turtle. (Roughly 10k catches for it overall) After i was done i logged on my shaman who was at kara no mount, logged the warrior also parked outside kara got the mount. (Roughly 400 kills.) Went on my druid and did Onyxia because of the sheer luck i had Onyxia mount dropped. Wasn't even surprised. (roughly 100 kills)
Found the screenshot If you look at the time you can see it's 02.08 so maximum time that could have passed was 2h 8 minutes i i cought the sea turtle 00.00. Also had a quick run by Skadi sadly that mount didn't drop... for another month.