> it seems now its even enough to just move the mouse...

The screen is redrawing a lot when you move the mouse around because of the selection highlight function, where the object under your mouse gets a pre-selection highlight on it so you can know what will be targeted for selection when you click down.

If the dropouts kind of shift randomly it's my best guess that your machine is getting overheated and your video card is not working properly when it's at a high temperature.

Some possible things to help reduce that here:
http://machmachines.com/macbook-pro-retina-overheating-fix-now/

- Michael