This should be "revisited" with the 14.6 Catalyst drivers.
Also, could you do one on the "lowest" settings. (Needs to set both the video and display, and possibly alter the game XML configuration for some of that.)
Also, the game should be launched with the watch_dogs.exe file, by creating a shortcut with the "Target" appended with " -disablepagefilecheck", for PC's. (Seems that is a console-only feature causing some issues.) Not sure how to ensure that the game launches with that switch, any-other way.
Also, "Check file integrity", before launching, then "defrag", because the download scatters file fragments all over the place, as it downloads. Then launch it with the short-cut. Then you may have to set it back to full-screen, because it seems to go back to "windowed", even though the settings tell it to display full-screen.
Another odd thing. Setting all volumes to 0, even the hidden one in the XML setup for "globalsounds" which seems to only for music-songs and some random other sounds... still does not turn off all sounds. There is one group of sounds that do not obey any volume settings. (Might be part of the culprit lagging issue. How many other things "set in the settings" are not actually obeying the settings.)