Those of us who are into pet collecting know how difficult it is to get a Minfernal or a Giraffe Calf, to name just two examples. It takes hours, days, sometimes weeks of religious camping in Feralas or frantic rushing across Southern Barrens before we even get a chance to see one. Then there's the whole CRZ competition, and people getting there just a fraction of a second ahead of you. That's fine, too, that is how the game works.
However, when - after all the time and effort put into it - you finally do get your precious pet and it turns out to be a poor quality one... it just seems like a really painful kick in the butt, doesn't it?
So please, make those really hard to get ones a guaranteed uncommon quality. I'm not asking for a rare quality, that should always be something you work hard for, but uncommon sounds perfectly reasonable considering the circumstances.