Everyone has a different experience villager hunting from what I've seen and read. Villager species that are real common to some are seldom encountered by others, and vise versa.
For me, when I used to island hop like mad (I don't anymore because I have all 10 perma-villagers secured. Gonzo, Boots, Carrie, Ken, Annalisa, Dom, Sprinkle, Pecan, Agnes and Tucker) the most common species the game rolled were cows, cats, koalas, cubs, octopi, hippos, dogs and rabbits. I barely would come across hamsters, deer, eagles, ducks, pigs and alligators.
I can't tell you how many times I've found some of the most desirable villagers such as Lucky, Ankha, Raymond, Beau and Marina.
In total, finding my dreamies took about 400+ tickets (How Dom eluded me so... And I was half asleep too in the middle of the night, I could have easily missed him)
It seems that the least amount of villagers within a species are the most common, a good example being cows (4 total being Naomi, Tipper, Norma and Patty) and more infamously the octopi (3 total being Marina, Zucker and Octavian) then you have the alligators (6 total being Sly, Alfonso, Del, Gayle, Boots, Alli)
Meanwhile there are so many rabbits and cats that you definitely ought to bump into one at some point, but really it all comes down to our good old merciful friend RNG.
The real prizes, IMO, are the non-Amiibo villagers, those being the sole 8 introduced in NH: Sherb, Judy, Audie, Cyd, Dom, Raymond, Megan and Reneigh.
I'm grateful to have all my dreamies now and don't have to island hop anymore, except of course to gather lots of materials on mystery islands. But at the same time I'm sad I can't bump into random villagers anymore, because I don't have an empty plot and never really will. There was a big thrill and excitement seeing all sorts of villagers and getting to know them. Because of island hopping I got to meet Gonzo, Boots and Carrie, and all the other welcome Amiibo villagers, and more importantly it's how I reunited with Annalisa after losing her way back in NL.