I've seen polls that still hold GWB accountable for the economy (but maybe those are people that are likely to vote for Obama anyway). They are also very weary of both the wars and any possibility of a war with Iran.
But you are probably right on the focus groups. The Bain attacks have some resonance in the states they want to win, whereas attacks on foreign policy are probably not as nearly effective.
That seems to be what they are building to. They're starting to make the transition to focusing on Romney's policies, after working to define him and hammer at his business experience. Once the policy points are made, I think they'll follow up with the GWB connections closer to the end of the election, when the scare factor could be more effective.