GNaschenweng,
The issues with Retina display are fixed in the latest MyEclipse 2015 release. If you are already working with MyEclipse 2015 CI, then please go to Help > Check for Updates and update to the latest release.
You can also download the latest installer from here : https://www.genuitec.com/products/myeclipse/download/
Let us know if you see any issues.