No, certainly not. However, he made a terrible decision to leave the flight deck at all, considering the weather up ahead.
I don't have all the history of the Captains prior flights/routes, but this was not the first time he had made the Paris/Rio/Paris flight. It was also not the first time the ITCZ had a few storms. It was also not the first time the Captain had taken his rest period for the second 'shift'. It would not surprise me one bit to find out that this was standard practice.
Is it the considered opinion of the majority, that the one person who would have brought AF447 through this event was the Captain? So why bother with the other two? Were they there as highly paid seat warmers? I presume A/F figured they were competent crew.
A pertinent question - why is it assumed the Captain would have done a better job? Is there any special reason to assume the Capt has more hand-flying in cruise experience. Or did he simply have many more hours sitting in the cockpit watching the autopilot?