i didn't go for dragons the last 2 or 3 weeks but i know what you mean.
but i don't think it's abnormal. sometimes i used the whole daily gain of stamina and refilled 3-4 time to get 4 or 5 dragons.
and its everytime the same:
i need 4 more dragons and start running. first 6 runs: no dragon at all. then i get 2 at once. another few runs without one before the semi-last one appeard. "one to go" i think... and then comes the frustration. 1 refill and one more refill and another gem burned down... and suddenly, the first run with the last refill i get 2 dragons at once again... so one more dragon than i need -.-

long story short:
i hate farming dragons more than farming manyus D: