The upgrades that say, "Hunters are more effective" seem kind of a waste of resources if I'm using Mints. Basically it seems like all of these are just there for people who use auto hunting. Is there any hidden benefit?
Nope, it is just for better hunting results. So if you always use the Mint building, you don't need to upgrade it. But you'll find yourself in some abundant catpower sometimes, and you can easily send hunters. There is no hidden benefit at all. Except that hunting is better.