I finally got Aithon in 4th day of 2.5,i kept farming Ifrit all days on DF and got average 7-10 win per day(ppl still sucks at ifit ...).so from roughly 30-40 win i saw 3 pony drops and i won the 3rd roll.i gonna say 10% drop rate is sound about right.

P.S. .Fire Pony is the only Primal Mount I always need so I won't bother farm all others 5.screw the kirin Mount !!!