Got a chance to try the new dynamic difficulty changes and they are still less responsive than 2.7.5.
I got some numbers this time, started up a game and ran both at dynamic intensity:
2.7.5 stabilizes during game at ~270MH/s and stays at I=6 (Game graphics only slightly different than no mining)
2.8.3 at ~325MH/s and stays at I=6 (Game graphics are noticeably choppy and playability is significantly affected)
    Setting the intensity manually to I=5 results in similar performance to 2.7.5, but obviously the point of d is to not have to do that.

I should also mention this effect is noticeable in other applications than just games, like videos.

For now I am happy with 2.7.5, just thought I would post my results to help out whenever time comes to do some more changes.