This bug occured when fighting Medreth and the cowled cronies:
When only Medreth was left the game slowed down immensely (I did not use the "slow" mechanic) with framerate drops and everything.
When Medreth finally hit the dirt the game instantaniously "fixed" itself and went back to normal speed and the framerate cleared up.
It was as if the game tried to process a lot of data, or perhaps memory got filled because the battle took quite some time (I was being dumb)
Additionally, here is some information about my PC that might be relevant:
BIOS Date: 08/29/13 11:00:49 Ver: 43.02
Intel® Core i7-3930K CPU @ 3.20GHz (12 CPUs), ~3.2GHz
16384MB RAM
Windows 7 Professional 64-bit
DirectX 11
NVIDIA GeForce GTX 780 (Running in sli with another GeForce GTX 780)
1920 x 1080 (32 bit) (120Hz)
Drivers are up to date, using Geforce Experience and being very diligent at updating them constantly.
I can also deliver full dxdiag if needed.