Okay, so I do lab tasks often, so I obviously need to get a bunch of Pokes to be able to complete them. So I go to their proper area (using a guide, of course so I make sure they can be found there) and find out that whatever pokemon I'm supposed to hunt, it automatically becomes the rarest thing there. Anyone else have this problem or am I just super unlucky?

Id say your just unlucky but i do know what your saying the same thing happens on the random swap too,the pokemon you want the most seems to be come very rare lol but just keep going with it and you'll get the pokes in time :)

I know Zapdos, im trying to get a shiny in the random swap thingy but still no luck, hope it works...

You definitely get all mixes, but when you are able to collect extras, it makes it easier later one to hand in the task. So you can either buy the Pokes or just continue trying. Good luck!

I would say that zapdos is right, the reason its seems unlikely to find one is just a mine trick. The rates are still the same but you need to realize how many pokemon you can find there. When you focus on trying to do something it seems harder but it is really the same thing.