Finanlly i managed to get the LOD working. The good thing is, that it works even better then expected, the bad thing is that i cannot load a 16k*16k texture At least i finally know why someone on earth would ever buy a quadro card.
The biggest problems i have (once worked out how the shader communication works) is Tessellation with 3 Vert’s/Patch. Even if it looks ok in wireframe mode, it causes lots of artifacts in Texture mode. However, once i switch to 4 Vert’s/Patch everything worked like a charm. It even works more performant.
For terrain, tessellation works pretty well. It allows a extreme wide sight and smooth transitions to very detailed terrain.
Next goal, tessellated water :)