I'm getting ready to quit this.
The uneven hatch rate is so infuriating, especially for 5km eggs. I've hatched many eggs and out of 41 possibilities, about 80% of my hatches are Ponyta, Nidoran, Sandshrew, Paras, Growlithe, Bellsprout, Poliwag, Krabby, Staryu, or Psyduck.
Those are some of the most common 5km hatches. And yet, other common hatches like Ekans, Tentacool, Meowth, and Vulpix, I've never received from an egg. Maybe the Pokestop you pick an egg up from does have something to do with what hatches and can alter base hatch rate. Because my most frequent hatches (Nidoran, Paras, Poliwag, Staryu, Psyduck) are all fairly common either in my area or in neighboring areas.