Over in the publisher’s forums, an update from Ubisoft mentioned that “if playing single player, we suggest that you disconnect from your internet connection (wifi or network cable). It could potentially improve frame rate.”
Of course, when one is grasping at straws and are desperate enough, one is willing to try anything. Those who have already given Ubisoft’s suggestion a go realized that there really isn’t much to continue from here, as the perceived frame rate does not seem to come any closer to the target 30fps”.
Digital Foundry mentioned, “We’ve now tested single-player with the console online and offline, and report no game-changing difference to the overall experience. In some cases, running offline is faster, while in others performance is the same or lower. We’re inclined to think this is just down to the variation in engine load between the two sessions, and there’s little evidence to suggest that it brings us appreciably closer to the target 30fps.”