Hey, you've got a couple of problems with your node setup. Mainly, you cannot use BSDF or BSSRDF ouputs as factor or color inputs. Currently your SSS nodes are not doing anything. This is because BSDF and BSSRDF are computed in the render. They are instructions that tell light how to behave when they hit a surface, its not like Blender Internal where you can use them into others sockets. These outputs can ONLY go into mix shader nodes, add shader nodes, and material surface output.
I have not experimented with SSS much myself, so I can't give you a proper node setup for it off the top of my head. But it does not override what your basic material setup ought to be. It should be a diffuse mixed with a glossy, with the mix factor being a fresnel node with the appropriate Index of Refraction for human skin (which you can find on google.) ANY material that is going to be photorealistic has this at its core. Everything has Fresnel
http://filmicgames.com/archives/557I do not know if SSS is mixed in, added in, or replaces the diffuse or glossy, but you should be able to find that on google or the blenderartists forum.