Post by Porcell
Block Value/Rating gear is used for tanking lower level instances so you take 0 damage, for soloing lower level raids so you take less damage, for tanking heroics so you take less damage and do bigger shield slams, and for PvP. I use a couple of pieces of Block Value gear in my heroic tanking set; that's about it.
There's a lot of misconceptions in your post about gearing, and it's such a common misconception that it's frustrating to answer.
When it comes down to it, you don't really have a lot of choices when it comes to gear. You have choices on gems, which we have covered a lot (Stamina in Blue, Def/Stamina in Yellow, Dodge/Stamina or Expertise/Stamina in Red). With gear, you just don't. A gear upgrade is pretty much always going to be a clear upgrade. There's no decision involved. Once you get that upgrade, gem it appropriately and wear it.
There's not much to decide. You aren't going to find a piece of gear with Defense, Parry, and Hit on it, and say to yourself "You know what, I don't like Parry, I'm going to wait for a Defense, Dodge, and Hit piece to drop." It's not going to happen. There isn't that much variety in the same tier level. If you are currently wearing a 245 bracer, and a 251 bracer drops, it's most likely going to be an upgrade and you'll be able to see that immediately.
Don't avoid parry. Download an addon like Ratings Buster so you can see how much avoidance a piece is actually going to give you. A number of times I've upgrade a piece of gear and gone from a piece that gives me 0.80% dodge to a piece with 0.85% parry. It has parry, but it ended up giving me more avoidance.
Now, sometimes there are choices in the same tier level. Maybe between the
ToC Crafted, the
Expertise Chest, or the
Tier 9 Chest, all of which are item level 245. In this situation, first you look at stamina. Matching socket bonuses, Crafted is 240, Expertise is 234, and Tier is 234. Using Ratings Buster is better, but for a quick comparison you can just total up the Defense, Dodge, and Parry ratings. So ToC is 209, Expertise is 174, and Tier is 207.
So which do you choose? Well, it would totally depend on what your expertise is currently. If your expertise is less than 26, I would go for the Towering Monstrosity chest. If you didn't necessarily need the expertise, then you have a choice between the Tier 9 and the Crafted. Does the Tier 9 give you a 2 piece or 4 piece bonus, or will it help you get a set bonus in the near future? If so, pick the Tier 9. If not, go with the crafted chest.