Just wanted to thank you all for all this great information. I just got back into playing wow, and started playing (dusted off *cough*) my warrior again (built him at launch!), and this gives me a good start on how to build up a nice tanking set (I currently have a hodge podge of crud). Thanks all.
As to the reforging mastery, do you still want to shoot for 20% parry/dodge? I think I am sitting ok now at 20% parry/dodge, with the rest going mastery, but am not positive as I keep reading one way or another.
Imo I'd say don't let parry/dodge go too far below 17%. I've got 14.64(18%) Mastery myself, so all my tanks stats are: 20.73% Dodge, 20.85% Parry, 38.30% Block.
Looking at your gear, change some of the expertise to mastery that you forged to then I'd call it good.