Everything is done in ratings, 23 defense on a ring is overpowered, 9.72 defense on a ring isn't, when you hit lvl 80 the defense on your old gear will not translate into the same amount. This is less critical on a stat like defense, but think about critical strike and what new gear without the rating system would be like.
Oh, I understand the rating system, but it doesn't make any sense on an item that the required level to equip is also the scaled amount. When would it be the full 23 rating, and what's the point of listing it because you can't equip it until 70? It just seems really silly on an item like this why wouldn't they just say "increase defense skill by 9.72" because that's all you would ever receive from it. Know what I mean?