It doesn't look like chainamail to me, I'm guessing the clothing is just designed in such a way as to make it look like the wearer is wearing two layers of clothing, but it;s actually one piece. I don't know this for certain, of course, but that's what it looks like to me. Either way, the image doesn't prove anything, because we can only see what the character looks like, we can't see his actual inventory screen, and until we've seen that, we can't really be certain if what looks like it might be two seperate pieces of armor and clothing are actually seperate or just one piece that's designed that way.
It's an old build because that trailer was really made months ago, when they were preparing for the first announcement. The trailer with the dragon is just the long version of the trailer they showed at the VGA. There's no way they could have the final build for that trailer. The next one will probably look way better.
Obviously it's not a finished build, but that still doesn't mean everything in the trailer will look better in the final game. Did Oblivion look any better upon release than the official gameplay trailer? Or the early screenshots? No, in fact, it might be argued that it looked worse. Just because the game isn't finished doesn't mean every single thing will change in the final product. Obviously, some things we see now MIGHT be subject to change, but it's probably best not to assume the game will look significantly better when finished unless we're shown anything to indicate it will.