For those of you who don't know much about tanking, we're going to talk quickly about a stat that won't exist in Cataclysm. This lowly stat is called defense rating, and it's something that tanks need quite a bit of. The nice thing is that it's on just about everything that tanks wear, which means at higher gear levels, we've got it coming out of our ears. The primary point of this stat is to reduce the critical strike ability for incoming melee hits from the standard of 6% to 0%. Druids currently don't need this stat, as they've got a talent called Survival of the Fittest, which means that bosses don't need to drop defense leather.
All in all, the stat is kinda boring, as while it does still do nice things after you reach the defense cap of 690 rating (or 540 skill), most people don't bother with it and stack stamina or other avoidance. So Blizzard decided that they're going to get rid of it.
Around BlizzCon 2009, we were told that the crit reduction we formerly got from defense rating was going to be tied into things that were available to all members of each tanking class. Examples used were baking it into Bear Form for druids, Righteous Fury for paladins, Defensive Stance for warriors and Frost Presence (or rather, Blood Presence in Cataclysm) for death knights. That means that if a retribution paladin or arms warrior wanted to tank, all he'd need to do was swap to vaguely appropriate gear (or just over to a sword and shield), pop his respective abilities, and away he'd go. That's not how it appears things went down, though.
With the NDA now lifted, we've been able to see what they've decided. At level 40, you can choose to talent into Survival of the Fittest (three points) for druids, Holy Shield (one point) for paladins, Safeguard (two points) for warriors and Improved Blood Presence (two points) for death knights. The reasoning behind this appears to be one of health pools. With the re-itemization in the expansion, non-tanks will have a higher stamina budget all around and incoming damage even if you are critically hit won't one-/two-shot you.
So this means that non-heroic dungeons should still be tankable by non-tank-specced players, leaving heroics to those who have put more dedication into that role.
However, one little discrepancy that I've pointed out but glossed over earlier is still about those talents. In order to be crit-immune, you must be level 40 for a paladin, level 46 for a warrior, level 41 for a death knight (yes, I know they start at 55, but 32 talent points worth in the blood tree), or level 37 for a feral druid. This might cause a small bit of trouble while leveling through Scarlet Monastery and honestly doesn't matter in the grand scheme of things when you're dealing with 76 talent points at level 85.
However, perceived differences are still differences in the community. There have been many flame threads from DPS specs comparing how much hit or threat reduction one class gets compared to another or even how many talent points must be spent to do it. I have a feeling that we're going to see the same complaints coming from the tanking community.
One possible solution to this would be letting the first point convey that 6% crit reduction while the other features of that talent scale appropriately points. This would mean that all four tanks would be able to achieve the same needed ability with the same dedication into the talent tree and thus at the same level for druids, paladins and warriors.
As will be repeated over and over for the coming months, we are still in beta, and all of this could drastically change or be baked into other features of the class. The crit reduction could be changed in some way between now and launch, or we could end up listening to the tanking forum bicker back and forth about it while waiting around for the Deathwing raid in patch 4.3 to drop. For now, the magic 8 ball says, "Reply hazy, try again."
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion. From goblins and worgens to mastery and guild changes, it's all there for your cataclysmic enjoyment.