Saturday night I hopped onto the beta to screw around with Reforging and see if I could expect to block cap myself come 4.0.1. As many of you know, block capping means stacking enough block chance that ordinary hits are pushed off the combat table, which can pay huge dividends in damage reduction in certain situations. In Wrath, block capping was especially desirable for Heroic Anub in ToGC, allowing you to cheese the damage from the adds.
In Cataclysm, block capping is going to be amazing, if only because it’s going to be like having a cooldown up for every physical hit. With a successful block now reducing any physical hit by 30%, you want to be block capped. (Of course, that also means there’s a cap on our Mastery, because any further dodge/parry once block capped pushes block chance off the combat table, but that’s an issue for another day.)
So the goal is 102.4% total avoidance+base miss chance+block. How feasible in that in my gear set at 80?
Here’s where I was in terms of avoidance and mitigation when standing in front of the Reforger NPC.

46.42% avoidance + 5% base miss + 21% block (5% base + 16% for learning Mastery) = 72.42% avoidance and block. 29.98% short.
I then proceeded to reforge every feasible piece to mastery. Dodge converted over if there was more dodge on the piece, parry otherwise, and equipped the Heroic CTC and reforged that to mastery as well. I attempted to keep dodge and parry at least even, but I had so much more dodge rating that diminishing returns made it so I got a lot more mastery from dodge.
I then dodged over to a dummy, buffed, and put up Holy Shield. This is what I had:

At 42.03% dodge+parry I lost a total of 4.39% avoidance and gained 24.35% block chance from Mastery.
So, with the 42.03% avoidance + 5% base miss + 60.35% block chance, I was at 107.53% avoidance+block. 5.13% over block cap.
Not too shabby.
I’m actually at the point where I should reduce how much Mastery I have, because that 5.13% overage is just wasted block chance. To mitigate this I can swap the Heroic CTC for a stamina trinket, and then dial back some of the Mastery.
Actually, I’m really liking the extra control reforging gives us over our gear and stats. To be able to shuffle around secondary stats like this is pretty cool.
Anyway, once I hit 81 the ratings conversions will shoot through the roof and block capping will disappear until at least the first raid tier (at least according to the calculations done by Zarko in this thread) but I’m excited at being able to taste such amazing damage reduction potential for the next two months.