I had the Lync 2013 High CPU Usage issue probably a couple of years ago, also a colleague of mine complained of the same issue and then a few more came out. The issue wasn’t just the high CPU usage, in fact Lync was very slow and barely usable.
All we had in common, besides Lync 2013, was that we all had DELL Laptops. I was running on a DELL Latitude E6430/Windows 8.1 x64. The solution in all of our cases was to uninstall the IDT Audio Package (might be called IDT High-Definition (HD) Audio Driver).
That worked great and I then downloaded the latest drivers from the DELL website and all kept working just fine.