I feel like an idiot responding to this at all as this has been addressed at least dozens, if not hundreds of times before on these forums but...

There is NO duplication of work.  None at all. Every single worker is already working on it's own unique little piece of the puzzle.

Also:  why is everyone always trying to find some way that centralizing everything would make it "better"?  All of bitcoin's strengths are in it being decentralized and peer-to-peer.