Dungeon finder restrictions and the removal of choice
Stop me if you've heard this one: A feral cat druid, a fury warrior, and an unholy death knight walk into a random heroic dungeon queue. They get grouped up, they have no crowd control, and the group wipes on the third pull. This scenario wasn't as much of a problem in Wrath, where by the time the random dungeon finder was in place, most people were geared enough to AoE through almost every heroic dungeon. In Cataclysm, where crowd control is practically a requirement for many pulls in many dungeons, this type of setup is becoming a virtual death sentence to random dungeons. It's this setup that has inspired much of the clamor for extra crowd control methods for death knights and warriors.
Blizzard's directly addressed this now, but not in the way we expected. The March 9 update to the patch 4.1 PTR included a new feature: The random dungeon finder will now attempt to put DPSers of the same armor class in separate groups. This means that in theory, nevermore shall a fury warrior and an unholy death knight end up in the same random dungeon run. Sure, you may get a feral cat and an unholy death knight, but the cat has Hibernate, and in theory, your third DPSer will be someone like a shaman or a mage, who actually does have crowd control options that work on most stuff you'll come across in your average heroic dungeon.
But what this does is essentially "solve" a class balance issue through a completely non-class-related mechanic. Unless this was all simply a ploy to prevent people from having to compete on rolls for DPS loot, Blizzard's basically admitted that the lack of crowd control for certain DPS classes is a real balance problem, one that's exacerbated by stacking. However, rather than fix it by buffing the class, they've decided to target it by changing a completely separate mechanic -- something that, to the best of my memory, is a bit unprecedented.
Is this a precedent we really want to set, however? Class balance is something that is generally considered to be something you focus on classes, specifically. A class should be able to fit into a group on its own merits within the traditional role it fills, not because of a behind-the-scenes shuffling of the way puzzle pieces fit together. In addition, this tweak hardly solves the problem for guild groups who, while likely more able to try Cataclysm dungeons without major amounts of crowd control, still may have to make some tough choices about which guild members to take to a dungeon based on their lack of crowd control ability.
Raising the dead
The second major change Blizzard's made to death knight non-damage utility is granting us the ability to cast a battle resurrection. Now, admittedly, this isn't completely related to death knight utility, in that the developers have explained that they really do just want to make sure that battle rezzes are available to more raid groups without people feeling obligated to bring a druid. In that case, death knights getting battle rez can be seen a happy coincidence. We had a rarely used spell that had the flavor to be quickly revamped.
That said, it certainly is a rather timely addition for a class whose denizens have, at least in some part, been lamenting their lack of options in a dungeon group. Certainly, a battle rez has its uses. If nothing else, this way you can resurrect the healer when he dies because you couldn't crowd control that stray mob attacking him. It is primarily a DPS utility option, in theory, though skilled tanks will probably have battle rez on a mouseover macro for real emergencies.
But it's reasonable to say that a battle rez, in the milieu of 5-man dungeons, is no substitute for good, solid crowd control. There's a lot that go wrong between the time someone drops dead and the time a death knight can take a few seconds away from combat to resurrect him, especially if the stray mob that killed them hasn't been bought under control.
Blizzard's class mantras and crowd control
With all this on the table, I'll go ahead and make a claim: The addition of battle rez is the perfect example of why giving crowd control to a plate class is perfectly in line with Blizzard's philosophies, and in fact, the right thing to do for balance. Blizzard has shown that while it drags its feet sometimes, it does want to make sure that certain buffs and abilities are not completely dominated by a single class so that raids have (within reason) the ability to bring who they want.
Dungeons groups should be the same way. Just as battle rez is considered mandatory for raiding now, so is crowd control considered mandatory for most focused dungeon groups. Sure, we can do a little bit of AoEing, but if Blizzard keeps releasing new heroic tiers, even many guild groups (and especially non-raiding guild groups) may not reach the point that they can simply AoE farm every heroic. Considering that Blizzard has already given one plate DPS crowd control, it doesn't seem much of a stretch to extend it to the others. The solutions put forth in patch 4.1 so far have their merits, but they just don't address the whole problem well enough. I say again, just give us some crowd control.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.