You rarely use the same item on more then one class by the late game. While early on you'll be using one set for all the casters, one set for all the attackers, and one for the tanks, the items will become specific enough that you'll want the same stats for everybody who uses that item.

Right up until the endgame where you'll have picked one or two classes to specalise in, and you'll have items perfectly maximiised for exactly that class, but that won't matter as much.