Well here is a nice surprise. Ubisoft has just released a new update for the PC version of Watch_Dogs. According to the changelog, this patch improves performance on more recent models of cards (and as the French company noted, 770 and onwards GPUs will see better improvements). This patch will be auto-downloaded from UPLAY, and you can view its complete changelog below.
Watch_Dogs PC Update Changelog:
• Better performance on more recent models of cards.
– 770 onwards will see better improvements.
• Moved all resource creation to an exclusive worker thread.
• Changed technique used for updating texture mipmaps in Ultra textures mode.