If it were possible to design a proof of work system that effectively eliminated the ability to pool mining would that be an improvement or not?
this would bring up the barrier to entry for mining bitcoin several orders of magnitude. not good.
With pooled mining, anyone, even someone with very very bad internet connection and low hashrate CAN mine bitcoin. the fact that a handful pools each have a big slice of hashing power is not an issue, pools must behave they way there users want them to behave, Individual miners choose the pool they mine at, if they are unhappy with the way to pool operates they will leave an another pool.
not only does pool mining greatly lower the barrier to entry, I believe they will be instrumental in scaling bitcoin while keeping it highly decentralized.