I'm at 134 runs of Ravana and I've seen two birds; I brought the same idea up to my FC mates and they agreed. I would be all for having the turn in amount be something like 200, because at least that way no one can accuse them of "handing out" birds. I've had people in party say they saw 6 birds in 67 runs, and yet here I am at two after 100+. I get it's supposed to be rare and an achievement, but I feel like for whatever reason Ravana's drop rate is kind of ridiculous. I've yet to try Thordan or Sephirot so I can't really speak on those drops.