Here's a suggestion to help make shields (particularly ones that aren't raid loot) at least have some merit again.
Shield suffix: Of Striking
+ equivalent: +5
This shield contains a potent enchantment that bestows additional skill with one-handed weapons on anyone wielding it.
While this shield is equipped, all attacks made by the bearer receive an exceptional bonus to both To-Hit and damage rolls equal to the shield's enhancement bonus.
So a +4 Shield of Striking wielded in one hand, with a +3 Vorpal Longsword in the other, would make the longsword as effective as a +7 Vorpal Longsword. That's some serious loving for our poor maligned sword&board friends - whilst it won't get their DPS up to the highest echelons, it will help to make it more respectable, particularly against any future mobs with extremely high AC.