Looking at the DK talents for Cataclysm now both intrigues me and scares me. The changes make them just far, far good.
Current state of DK tanks is that, they go down a path of their choice and end up with two cooldowns to blow: Icebound Fortitude for all specs, and Vampiric Embrace / Unbreakable Armor / Bone Shield for Blood / Frost / Unholy respectively [There's Mark of Blood but for most fights, it's really awful]. Looking at the Cataclysm talents, we see DK Tanks gaining this:
- Icebound Fortitude [2M]: %50-70 Damage Reduction for 12 seconds. The talent that boosts it boosts it by %30, and with the current glyph it can go up from 20% to %40.
- Bone Shield [1M]: %20 Damage Reduction, 3.4 charges. Interesting this with this ability is, it's not removed with things like Mimiron's Blast, AoE or Dots.
- Vampiric Embrace [1M]: 15% Health, %35 Increased Healing taken for 10/15 seconds.
- Dancing Rune Weapon [1.5M]: %20 Parry for 12/17 seconds
- Rune Tap [60/30S]: %20 Self-heal.
- Death Strike: %17.5 health gain per strike and creates a shields that absorbs the same amount.
- Will of the Necropolis [15S]: Below 30%, Blood Rune/Rune Tap is refreshed and DK takes %8 less damage for 8 seconds.
DRW/Bone Shield when spammed together will highly increase the DK's avoidance and thus make each Bone Shield charges a lot more worthwhile.
IBF/VE combo will allow DK to have a lot more health, to receive a lot less, and be healed as if the healers had gear one tier higher.
Of course, when spamming all at once, you'd become as good as immortal, and if it's way into the fight with no problems of threat, but just a "GOGOGO DPS KILL IT NOW" scenario, you can save all your Blood runes for self-heal, DS for heal and shield, and pop Empower Rune Weapon for even more DSes. I can easily see a DK tank surviving a good 20-25 seconds even under current raid-scheme where damage is high and imminent, without a healer.
Of course, we don't know much about the raiding scheme in Cataclysm, but a nice comparison is other tanks. We currently have access to Druid and Warrior talents, and from what I've checked, neither classes pack the amount of CDs the DK has.
But that's not the only selling point of DKs. DK tanks have traditionally been the highest-DPSers in a raid setting, simply because all of their threat (Aside from Icy Touch for the moment) come from their DPS abilities. They're the only class whose Tank and DPS abilities do not change at all. This might come to change as a matter of fact, with Heart Strike being a tank-only spam now, as well as possibly Death Strike, these abilities might [and should] lose in their high damage output punch to stay balanced with rest of the tanks.
Furthermore, I sincerely hope Death Strike's unbuffed healing is no longer %5 per disease. That's just way too much. As you can see, 2 diseases bump this to %10, talents bring it to %17,5 and then the same talents give DS an absorb shield for the same amount. That's just.... overpowered. For comparison again, look at the Rune Tap talent. For a Blood rune, it gives %20 health, 30s cooldown. Death Strike costs Unholy/Frost (so 10 seconds cooldown for all it matters), gives %35 health, half of it being absorption. And any tank worth its salt can tell you %17.5 healing/%17.5 absorption is better than straight up %35 healing, because you can only heal up to full, but absorption will also increase your health effectively by %17.5 past %100 health.
Are DK damage mitigation going to be completely balanced around the fact that Blood Tanks will be vampire-like, so even with all these self heals, they're only going to be having their health globes up like a Warrior's? In other words, will the inherit damage reduction be lower compared to other classes so that healers have to heal the DK for the same amounts? I really think this is a slippery slope.
Personally? I'm in all likelihood going to be a tank in Cataclysm again. Currently, I'm browsing over Warrior and DK talents and abilities to see what will be the best. Now that Warriors are losing their monopoly on both of their shouts (Their Commanding Shout will be the same as Priest Fortitude, and Battle Shout will be the Agility/Strength of DKs and Shamans), I see few reasons to roll a Warrior but many reasons to keep it on with my DK.
Now, I'm not calling for "LOLNERF" here but this feels like 3.1 all over again when DK tanks reigned supreme and anything else wasn't really viable for Hardmodes. End result was, between minor patches and 3.2, DK tanks going from Uber to Lol and not being viable for... anything, really. Sure, they were tank when, for example, a Rogue was not. But most guilds didn't support a DK tank to ICC 25M Hardmodes, let alone TotC where Warrior/Paladin block reigned supreme.
I would just hate it if Blizzard wanted to give a lot of toys to Blood DKs to win their heart for killing two other tank specs (as well as Blood DPS spec) only after all this ordeal, realizing the error in their ways to nerf them again to the ground. Note that I'm not saying they're erroneous, but the possibility is high from what I can see, and if these changes make it to live, I hope, hope we'll stick to them until the end of the expansion.
Edit: I forgot to mention, I thought it was on talent build. DS's Absorption comes from our 3rd Mastery stat.