I'm having the exact same problem. I'm playing through both a singleplayer and multiplayer world right now, and it seems some seeds absolutely shaft you with bear spawns. Our small server (2-4 people) has around 10-12 bears within a 1000 block radius of spawn. 2 of them spawned right next to our house. It's genuinely so bad that the bears are more of a problem than the actual monsters. It's to the point where we aren't even able to go in some areas because of how many bears there are (one valley has 3 currently).