Let's cut the BS.
Fatigue can, in general, play a role during long haul flying. But it is still a pilot's responsibility to handle it accordingly.
About a year ago two guys up front were fatigued when making a landing in Munich. They DEMANDED enough separation on the ILS to perform an autoland.
See this thread:
http://www.pprune.org/rumours-news/4...-into-muc.html
This is how fatigue should be handled if it occurs.
Probably was not the case here.
Besides, for an augmented crew composition:
"The longer the flight, the longer your rest period will be."