stencil shadows are very-very slow with non-very-low poly models, even if there is only one bone anim character in the scene (say over 1000 tris), use shader based shadowmapping (pssm or any other), and it will be fine.
I use 400 characters in my RTS scene, I can get 25-35 FPS in a level with buildings and trees, and a not simple AI, but with bone anim shader which requires a pro license (you can win one for free), but it requires to use LOD models carefully, and other optimizations, like decreasing the number of views. for example I had to remove dynamic depth and refraction views and keep only reflection for my water...