Having the AH to use allows you to get exactly what you need very quickly. Non-class specific gear can be shared amongst all characters, which is great at first, but in the long run makes it too easy to max yourself out, too quickly.
I think itemization should give huge boosts to the current class specific gear, and actually should go further. There should be iLvl 63 class-specific items for every class in every slot, even Amulets and Rings for all I care. And these class-specific items should have rolls that exceed that of the gear that can be shared. All of these class specics items should roll with main stat guarunteed.
By decreasing drop rates, and creating so many new items, it should extend the time that it takes for new BIS items to emerge.