Unfortunately the issues with OSX 10.11 are 100% an Apple issue.
Apple decided to lock down something called "kernel audio processing". Kernel audio processing is what allowed the VSL (and a number of other products on the market, PreSonus or otherwise) to function.
Unless Apple were to decide to reverse this decision, the VSL software will not function.
This, and the reason the VSL software is being discontinued, is outlined here: