Kepler is generally a strong architecture when the shaders are optimised for ILP. In this case all the cores can be used in any Kepler product. The only problem when you don't optimize your shaders for independent workloads, so Kepler will loose 33 percent of the theoretical performance. This is the case with GameWorks. These shaders just use 67 percent of the Kepler GPUs, so 33 percent of your shader cores will always be in idle.
Optimising for Kepler is really easy. There might be some workloads when it is not practical to find some independent operations for the idle cores, because of the register pressure, but many times this is not a problem.
The problems are the licences. With some specific codes NV won't allow the devs to optimize the shaders. They can see the source, but they don't able change it, and the original code will hurt Kepler. This is why some games don't run well on these products. Basically the licences won't allow the performance optimization.