LOL we've sucked Dundee in - he's now hardcore!! Remember this?
http://www.ironworksforum.com/forum/...ad.php?t=99640
I would go to 2 places:
www.elitistjerks.com
www.tankspot.com
For rogues EJ has a spreadsheet where we can figure out gear itemisation and all that junk. There's also a download called RAWR (google it) which helps with that. If you're interested in the maths though EJ and Tankspot should have that, EJ is one of the best known theorycrafting sites out there.
Back in TBC, I thought the magic defense number was 491. It may have changed in WOTLK.