I wouldn't recommend using that driver version with the Radeon 6850. That driver release was mostly about the Radeon 7xxx cards with GCN GPUs. IDK if this is the cause of your problems, but it might be. Also, what version of 12.11 did you upgrade to? Last I heard, there were four versions.
First of all, the driver you are talking about is still in beta stage. Therefore, you may see some anomalies with it. Furthermore, this driver is said to be being developed especially for the 7xxx series. This does not mean you cannot use it for 6xxx series cards. But you should not see any performance drop, either. It could be that the driver is in beta stage. Uninstall it and reinstall it. If still no joy, use CCC 12.10, instead.
Personally I wouldn't be looking to update a driver any more if I has a 6 series card. Not unless it had a new feature that my card supported.
I'm using 11.8 drivers as there are no worthwhile benefits of newer drivers to my card. (5850)
I'm not (obviously) up to date with the situation with the 6 series cards and drivers but historically we are at the tipping point where it becomes, as you have found out, a hit or miss affair as to if we get increase or issues with older cards and newer drivers.
I uninstalled and then installed 12.10 and I am still seeing the huge drop. So I am just going to uninstall and switch back to drivers 11.7(the ones I was using previous to this). Thanks for the help guys.