My dk is a blood tank, currently is 1/5 Heroe's and 2/5 Valorous Scourgeborne Plate with 30.6k hp unbuffed, 43 avoid, D-capped, 25k armor

he does well in groups, i tank naxx and no-one complains.  as you said you can do dps, tank or pvp in all 3 specs.

i found frost quite boring and i enjoy the blood health boosts :D

blood has no migitation and doesnt give any AOE other than the basic abilities. frost has howling blast, which does double damage when target has frost fever. 3% added chance for enemies to miss, unbreakable armor, lichborne, and the haste party proc are ALL good for tanking and groups in general. blood can self heal a bit but ive tried tanking it doesnt do squat when mobs are hitting that hard. im a blood frost hybrid 27/36/8. (i think the math is right) i have unbreakable armor but i didnt see hungering cold worth while.

go frost. or stfu.

blood has no migitation and doesnt give any AOE other than the basic abilities. frost has howling blast, which does double damage when target has frost fever. 3% added chance for enemies to miss, unbreakable armor, lichborne, and the haste party proc are ALL good for tanking and groups in general. blood can self heal a bit but ive tried tanking it doesnt do squat when mobs are hitting that hard. im a blood frost hybrid 27/36/8. (i think the math is right) i have unbreakable armor but i didnt see hungering cold worth while.

go frost. or stfu.

lol dks are not considerred tanks the best of them gear and skill cant hold aggro or cant survive the only spec that can be considerred is frost and it does not compare to prot war or pally the 2 elite tanks imo u need a shield to tank even the almighty 70 druid tank is given a run for their money as they seem to be near extinct with the additions of many caster mobs which they dont stand a chance against

Blood knight's are not the best choice for tanking since they dont have the mitigation to tank a run w/o getting whooped. Many people think they are a good choice b/c of the parry chance and the added 6% strength and stamina.

Frost on the Other hand is a superb tree for tanking, offering Lichbourn and toughness and other telants to ensure you wont be a pile of armor scraps when facing a boss or mob such as the chance. My DK is frost and i can hold aggro just fine if not better then other DK or tanking class's.

Unholy imo is and should only be considered for DPS when in an instance not reliable for tanking. They dont have any type of mitigation other then bone armor the rest they rely on disease endurance and the added bonus to diseases.

The only issue that DK's are having is what type of gear work for there spec does Defence rating,Parry rating, and Dodge rating make you tank better or Crital strike chance rating,Hit rating,Haste rating make you do good damage fact is I am learning how to play the class, I have no issue with Blood I have to say Blood Aura is like another version of the Healing Stream Totem which heals like 2% of your health in groups everytime you damage Is very handy in Instances and raids.The problem with Frost is that it does Crit damage,Unholy does major DPS if you know how to use it right.

I've read several current threads from various people that all have documented a solid ability to tank as Blood and Unholy.  Some people are just idiots in WoW and because all the other classes have 3 seperate jobs for their talent trees, they are stuck trying to figure out what those are for the DK.  Truth is, any spec can tank as well as DPS.  Blizzards experiment worked out great.

the main probly i c is they dont have enough resilence aginst dmg heroics will eat up ur pathetic heals and they dont have aoe agro, but i personaly think frost is gimped and needs redone. also the resistance stacks up to 230 resistance btw

Frost has access to Talents Chill of the Grave, Rime, and Endless Winter that makes your assumption about Frost no generating enough Runic Power false. With Blood of the North and Blood Tap, Frost can literally spam Rune skills to generate unlimited Runic Power. They are the only Talent Tree that can effectively use both Frost Strike and Rune Strike flawlessly.

I love Unholy for reasons of my own, but I cannot deny the effectiveness of the tanking ability of Frost. The one thing I dislike about it is when fighting against frost or water elementals when its base damage capability is gimped due to elemental immunities.

Blood cannot tank, regardless of what you have experience, Frost can tank better. If you look at the talents in Blood, there's very few that improves your tanking ability...namely, Blade Barriers. Rune Tap and other "semi-healing" talents aren't that great in raids. You're better off using that talent points into pure DPS build.

Blood is good at leveling up, but after that, you should either spec Frost as main tank, or Unholy for AE DoTs.

You just have to view this objectively, as a raid healer, who would you rather tank, a Blood spec who will constantly need healing because even though it can self-heal, it's not sufficient enough or Frost spec who rarely needs healing due to it's superb resistance to almost everything?

It's not my intention to put you down, but you need not to insist a DK spec and it's not made for a tanking purpose.

@Nikkadaem:  That is intended.  There isn't supposed to be a single role for each talent tree for a Death Knight.

While Blood has the abilities necessary to keep themselves alive and things that do help with threat generation and tanking; I do not agree that blood is a viable tanking spec by itself.  A friend of mine told me about a hybrid that he came up with in which I have currently implemented.  Death and Decay, Howling Blast, in combination with icy touch, plague strike then pestilence to spread it to the other mobs and then blood boil.  With this hybrid and even when I tanked as full frost I didn't have any issues with holding aggro.  A big problem that up and coming dks have is that, as good as the gear they get from finishing all of the starter quests is, it isn't tanking gear.  On my server, a lot of people have tried tanking as something other than frost and it hasn't gone over well at all.  People have started not even looking for dk tanks; fortunately, I have a good enough reputation with people that they know I can do it.  Well, what are the problems you ask?  Just because you decide to dip into the frost tree to get the armor contribution from items and have frost presence on, does not mean that you can successfully tank an instance.  I bought gear off the AH to make myself uncrittable at 70 and went from there; the complete cobalt set is good for that; however, in uthgard keep, the last boss, in his second phase, still hit me for 9k.  In frost are talents that were mentioned in the first thread that you must have; there is no getting around it...pallys and warriors have shields for mitigation; druids, a ridiculous amount of armor and hp, dks.....parry, miss, and dodge.  When a dk gets hit there is no [x amount of damage blocked], you take it.  I am not saying that the above person is a liar at all; they may have an easy time of it being full blood.  My hybrid is 35/36/0.  With this spec, I get more attack power with the heavy armor, the mark of blood which is a life saver, veteran of the third war, blood worms, blood aura, and rune tap....everything that can increase damage and keep me alive if a blood mob gets in that big hit...frost side, we have lichborne, improved icy talons, frigid dreadplate, runic mastery, and unbreakable armor.  This combination of protection and runic power generation from the frost tree and the increase life gain and damage from the blood tree; combine into a viable tanking spec for those that don't want to go completely frost....Deathchill in the frost tree, when used with howling blast, activates bloody vengeance and procs based on how many mobs got hit with the howling blast, so three or more mobs get hit with it...two spells and it's three procs for the price of two abilities...oddly enough, I wish they would have given something for the death and decay cooldown by itself, I only use death coil when I have nothing else to do with runic power.  Chilly of the Grave combined with the glyph of icy touch will eliminate all problems with runic power generation; I stay at 130 at the end of each fight because of it.  I will be happy to give out the specifics of the spec if anyone is interested and wants to try it out.  Personally, I would love to not have to go down the frost tree for tanking, but with this spec, not only can you tank, but you have the frost aura and blood aura, and improved melee haste that will make raids keep inviting you back again and again.

Sorry added my comment on your profile page, but you should have at least 5 talents on each tree, dodge = unholy, when blood runes on CD % parry = frost, and then pretty much what ever you want the others in, ohh also you got to get the one that does the 15second reduction on CD for the AoE spell forget what is called (lol) i think its first line unholy in the middle (i think) but you must have frost aura active for tanking, +5 threat and armour and hp buffs

@althos, i completely agree, my 78DK has been kicked out of many groups for not being a tank while in blood spec. regardless of being 5/5/5. It's extremely annoying the ignorance of some people.

@nikkadaem, There is no way blizzard should "fix" the trees to be better defined. that would defeat the whole purpose of being able to tank in any tree. it's supposed to be balanced and based off of playstyle. Which is basically why i rolled a DK.

I'm thinking that in forth coming patches Blizzard needs to make a few changes to better define the rolls. From what I've seen thus far each of the specs is pretty balanced with the other. There isn't a clearly defined roll for any of the specs. It's a bunch of gray matter floating around in space. My DK is unholy, just because I have a holy pally and I thought it would be funny to name him Darth and give him the exact same look as the pally. I'm really enjoying unholy, but plan on trying the other specs soon. Blood is my first choice.

while ive not tried Blood spec for tanking i have spent a day as a Frost tank and far longer as an unholy tank, i hit 80 not too long ago (3 days) i tried tanking 4 heroics as Frost and aside from single targets and all the aoe stuff to try and hold threat like DnD and HB i couldnt stop the dps taking threat i didnt find any problems with runic power always had enough but not too much, so needless to say i went back to my unholy tank spec and having done that the only way i loose threat to a dps is if they manage to pull it away from me (got a certain DK friend that likes standing off a bit and using Death Grip, fine by me but if he gets the healer killed its his fault)

Cant say im that interested in blood atm but i may eventually give it a go till then i love my ghouls and aoe spammage