Same issue happens for me on MBP retina 13 inch. Looks like jumping the ship to Parallels may be the only option.
For those that suggest using Lync 2011 on Mac instead, the screen sharing on Lync 2011 for Mac is WAY slower than screen sharing in Lync 2013 on Windows VM.
Please keep this thread updated with any possible workarounds/ options.
VMWare - Are your engineers/develpers listening?? Any response?