Bump. It actually feels like a bug since the behaviour expected by the user would be DPI awareness. After experimenting with an older Juce version and this High DPI support for non-plugins on Windows i found that it is generally possible to make the DocumentWindow DPI aware when launched by a plugin but unfortunately it destroys the correct behaviour of the plugin editor.
@reuk (or others in the team): Would it be possible to conceive of a fix for that inside regular juce?