I did four or five. Got more or less nothing. Doubloons dont drop with any kind of predictability, the rewards are all RNG, the vendor is a joke since you can run them back to back and get no doubloons, theres no use in running normal since you get close to zero , doing the higher difficulties means a repair bill, azerite and nothing else.
RNG means you can run these on heroic or higher forever, then NEVER see one of the mounts.