I think it depends a lot on what kind of server you are trying to do. You can always just take a look at a creatures list. What I think is more important is the purpose of your hunting zone.
If you are doing a (real) RPG, then you should care more about the space and place a hunting zone is taking. It should be more or less consistent on why it is there at all. The traveling time is also something you should take into consideration. For this kind of maps, you could make different zones to fulfil different purposes and then variety is important, making every one of them special in some way.
If your map is "teleport based" then you should care more about the number of hunting zones you are going to give your players. For example, dragons is something that I'd everyone goes to hunt once in a while. So having two or more different dragon zones each with its own thematic would be a nice touch. Also, don't just put idk... Dragon Lords in a "dragon lord cave", and please don't put one every 10 sqm like you were counting. That makes the hunting place just monotonic (a.k.a boring). Think of ways to tweak things up.