I play with Raging Barbarians so I'm not sure if my feedback is valid, but I feel the animal spawn rates are about okay right now. I liked your last tweak, which I feel improved the frequency of "useful" animals (that have herd buildings), although some are still fairly rare primarily because the tiles they can spawn from are rare (llama especially, but also camel and pig). Previously, I would be lucky to see more than a half dozen of a given useful animal, to say nothing of whether I could attack it before an AI hunter did so, and whether I'd manage to capture it depending on how well-promoted my own hunter was. (Previously I had been editing the SpawnInfos manually to make all basic tiles valid for spawning, and to remove the region limits, on said herd animals. This tended to spawn way, way too many animals, so much that the AI couldn't deal with it. This was without using the spawn rate modifier.)
Some of this might be the region-specific spawns but I tend to play pangea maps so have access to all regions.
As an aside, maybe a game option to disable the region-specific spawns, and a second game option to disable the tile-specific spawns (in this case, with a corresponding large reduction in spawn rate, given my experience with the above)? But I don't know how much work is involved in adding such things.