You could improve the ability to hit by making the weapon cut better (e.g. a sharper edge), but OB is more versatile than that. You can parry and convert that OB to DB. So I think generally it's better to think of it as a weapon with better balance, better design, that is easier to move the way you need it to move. Better materials give the smith more freedom to balance the weapon better, you don't need the big heavy blade to be structurally strong enough, you can have a lighter blade of the same strength and put more of that weight into the pommel to balance it out.
That could apply to a shield, too, of course. You want it to be stronger and lighter, although not too light since it needs to have some inertia to block with.
What does the ring do? Presumably you're not actually blocking attacks with the ring. It could make you faster, quicker, more aware of attacks. It could make you harder to see. It could create a force field around you that slows down attacks. I think the issue here is mostly how those bonuses stack. If the ring makes you harder to see, it shouldn't stack with Blur or Aura. If it projects actual force, maybe it shouldn't stack with a Shield spell. Etc. By specifying a particular spell effect instead of a general bonus, you make that explicit.