Not sure what problem you're complaining about regarding the Retina display. I'm using a Retina display MacBook Pro with Fusion and am having no troubles with Retina. I have a 13" machine, as well.
Set the Mac retina resolution to the highest resolution (1680x1050) and then, in the Fusion settings, choose the Display settings and make sure the "Use full resolution for Retina display" is NOT checked. If you leave this box unchecked AND change your Retina resolution on the Mac to be higher than the default Retina setting (System Preferences >> Displays >> Scaled), which corresponds to 1280x800, you will get an equivalent hi-res display resolution in the Windows VM.