Just wanted to toss my data into the pile
After the newest patch this is what i just got during a test run of the game in both Pseudo Full Screen mode and Full Screen mode. Both tests were performed at complete full (highest) settings SSAO on and Vert Sync Off, on London Sight seeing tour in a Spit. It was tough to tell but i think the frame rates would have been amazing if the cut off of the GPU could be corrected.
Pseudo Full Screen Mode gave me Slightly improved and steady GPU2 Performance with Slightly less Severe complete cutoffs of GPU1. Illustrated in the first photo attached.
Full Screen Mode gave me almost 0 GPU2 performance and increased GPU1 cutoff severity and i think it even increased the frequency of the cutoffs as well. Illustrated in the Second Photo attached.
Cheers