I had a similar question a while back and found this article. I hope that it helps.
Shield related blog entry, discussing block etc
And here is a working BiS list that may prove useful.
BiS List by Halandir
By no means do I want to hijack this thread, but in conjunction with this question, how far is too far when it comes to dropping block? I can get to ~25% dodge if I specifically gear for it, but then my block is ~14% and blocking about 1000dmg. I can balance things out by swapping a few items and get to ~23% dodge and ~18% block, but is it worth it?