Giant over-looked pro to this system:
Being forced to redo bosses each week (or at least choosing to) means more gear for the next set of bosses.
They're making the competition for world first less about which guilds have the most raid groups running (though I think doing that is good).
Generally, I think its a way to help even out gear-ups, and force more gearing up throughout the course of the raid. Basiclaly they are saying you won't kill the LK with ToGC gear, you'll need a good ammount of gear allong the way.