The spawn in my area changed a lot, but not with rares. It got flooded with rattata. I used to read people complaining about rattata and I thought it was funny cause i only saw 1 or 2 a day.
With the ditto update they are more common than pidgeys now, it's a drastic difference. So they have definitely changed spawns in some way.
Have seen more rhyhorn than usual too.
