One thing that we've been taught as tanks throughout most of World of Warcraft is that you had to be capped at something in order to not be insta-killed by bosses. Back when I started playing, this was referred to as reaching uncrushable. You would have to stack up 102.4 percent avoidance in order to push the dreaded crushing blows off of the boss's list of possible attacks he could hit you with. This also meant that all incoming hits were avoided or mitigated in some way, shape or form. That primary form was blocks, and abilities like Shield Block and Holy Shield at that time were custom tailored to this environment.
With the release of Wrath of the Lich King, crushing blows were deemed a thing of the past and bosses would no longer be employing them against tanks. However, we quickly had a new cap to deal with instead of that called the defense cap, aka reaching uncrittable. This meant accumulating 540 defense skill against raid bosses in order to remove bosses of being able to hit us with a critical melee attack. In early raiding tiers, this was a constant balance between gems, enchants and trinkets, as each piece of gear we accumulated could change how the scales tipped.
Now, with the 4.0.1 patch and the coming of Cataclysm, the developers have decided that the defense cap was also too fiddly and avoidance numbers in general are just way too high. So defense is gone as a stat and has been replaced with talents to provide our melee critical strike immunity. Also are gone the stats of both block rating to increase our chance to block and block value to increase the amount we block. For a shield-based tanking class, this leaves us in a bit of a pickle.
The debut of mastery
Thus enters our newest stat, mastery, which is all things to all people. Kind of. Mastery makes us better at whatever it is our specs are supposed to do. Protection is a tanking spec, so it makes us better at tanking by increasing our chance to block through the mastery Divine Bulwark. Not exactly block rating, but it works. We also now block 30 percent of incoming melee attacks instead of a fixed number based on our combined block value through gear. Holy Shield currently increases our chance to block by 15 percent while it is active.
However, after running some numbers, both the theorycrafters and the developers started coming to the same conclusion. After all of the nerfs to avoidance and block, it was still possible to reach the old block cap at which all incoming damage was mitigated. It would take a lot of stat reforging, gemming and enchanting to do, but it was still possible -- and Blizzard doesn't like it.
So, in an upcoming patch, we're going to get some reworking again.
Mastery: Too good for its own good
In essence, mastery was too good. We're expected to always be striving to reach that block cap throughout the expansion, instead of obtaining it straight out of 5-man content. If we can reach the block cap (102.4 percent in avoidance plus block chance) then we have no reason to work on avoidance stats any further. Encounters are going to be balanced around having well-rounded stats in avoidance, health and threat. If you're too low in any one of those, then you're going to start running into issues.
Part of the problem we were running into during Wrath going into Icecrown Citadel. Our avoidance had reached a point at which we could flat avoid most of the attacks sent our way; our incoming damage was bursty, and the incoming damage had to be increased to a point where two consecutive hits would kill us.
The solution, one that neither we nor the developers were fond of, was Chill of the Throne. It, like Sunwell Radiance an expansion earlier, was there to compensate for players having gear levels a tier higher than were intended at endgame. Wrath's issue arose from the fact that Blizzard kept adding additional tiers of gear for hard-mode raid content in addition to the different tiers that were already supported to differentiate between 10- and 25-man content. This caused a lot of gear inflation and is responsible for some of the absurdly high stats players are currently able to sport.
The Burning Crusade's Sunwell was literally a tier of gear higher than was intended. Black Temple was meant to be the pinnacle of raiding in its expansion, but because of the way raiding attunement worked (or more to the point, didn't), the additional raid was needed late in the expansion to fill the lull. Thus, players stats were too high for the content and needed to be brought back down.
Adjusting the paradigm
So, the paradigm adjusts to tanks getting hit more often but for less damage with each hit. This eliminates issues with PvE burst damage and gives tanking gear someplace to strive toward. There is no real "cap" defined yet for avoidance, because there aren't any real milestones to hit now. The old 102.4 percent is distant enough that we've no chance of easily hitting it; crushing blows aren't an issue; and we're already uncrittable, thanks to talents.
Does this make it harder to look at a tank's gear and see if she's set up properly? Probably, but most people were just looking at gear item levels anyway and not at gem and enchant selection when running quick dungeons. One thing it does provide is a little more wiggle room for preference. If you want to focus on being a block tank, then more power to you. If your focus is on threat, then go for it. Gear for your playstyle and talent setup and adjust accordingly. Just make sure you aren't focusing too hard on one aspect and ignoring another.
The Light and How to Swing It tries to help paladins cope with the dark times coming in Cataclysm. See the upcoming paladin changes the expansion will bring. Wrath is coming to a close and the final showdown with the Lich King is here. With Cataclysm soon heating things up, will you be ready?