Ok... after two days of fiddling and trying all sorts of stuff. I have FINALLY solved the issue.
The problem was, that the Amd Catalyst drivers DO NOT support Windows 8 (Well waddayaknow..). I've upgraded to Windows 8.1 and my framerates skyrocketed to 60-70fps on very high in games. Even the temperatures do not exceed 54°c on the CPU and 56°c on the GPU.
(Inb4 im a noob for even using Win8 instead of Win8.1 in the first place)
A big thank you to everyone in this thread for helping me out, as I would have been stuck trying the wrong things.