I think my first rare mount story was back in wrath when I started to farm ZG for the mounts. After just a few runs with a ret pally (I'm a mage), we saw the raptor drop and I won that. About a month later, ZG was about to reset and we hadn't run ZG yet and my friend wasn't on, so I found a random bear tank to go with me. I told him if the raptor dropped he would get it since I already got it. He said "oh ok cool, well then if the tiger drops I won't roll on it too, just to be fair". no raptor, but the tiger dropped! I told him that he could roll against me since I wouldn't have had a chance to run it before reset if he hadn't helped me. He told me "nah man, I told you I wouldn't roll on it, grats". sure enough he didn't roll on it, so I got the raptor and tiger within about a month of each other. a few days later, I found a guy that sold me the blizzard bear mount for only 5k.
Since then, I hadn't had much luck. finally got my white strider, then a few months later got my raven lord. didn't really farm the kara mount much, randomly went one day by myself in cata and it dropped. I occasionally would pester a friend who had ashes to help me get it in cata. we did it a few weeks but then kind of stopped. I asked him one day to go do it with me, we were just talking casually in vent when I hear him go "ohhhh shiiii--" and I was like "oh what did it not drop aga....oh...it dropped, nice." no one to compete against for ashes. just two nights ago our raid got called early so I told me friend "hey lets go get you ashes" it was his first time in TK on that toon (he had been before, but never really farmed for ashes). sure enough, the bird drops for him.