This is the spec im am currently useing
http://www.wowhead.com/?talent=j0EMqchcoZGgx00IbMhoZ0x
Let me just start out im used to maintanking 25 man raids, when im the first one into a group of mobs "trash" or on a boss, If i pull no one can get agro off of me unless they taunt. For trash mobs were talking about 5 plus mobs. At the end of the game i am a High dps tank, doing around 1.6 K to 2.2K dps for overall fights.
My general rotation is to pull with Icy Touch, when the mob gets in range use plauge stike, and wait for other mobs to get Closer then i use Pestilence, "now every mob in range is diseased" and hit blood boil, Blood Boil, and for some more added DPS I use Howleing Blast
IT>PS>Pestilence>Blood Boil>HB
Icy Touch and Plauge Strike are Dots, Pestilence Spreads existing infections from your target to all other enemies. At this point your doing only Dps But once your infections are up use Blood Boil. Blood Boil is the key to me never losing agro, it is a AOE taunt, that generats lots of agro.
I Try to save DnD for when someone other then me pulls, DnD is a DPS attack but on the go is a easy way to get agro
My Idealogy is Survivability > Agro > DPS. Survivability if your not going to beable to take a hit you shouldnt be tanking, Agro If cant keep everyone else alive your your not going to be a good tank. DPS the bouns of being a Death Knight Tank.
Survivability:
1. Frost Presence
2. Never Dual Wield, dual wielding decreses your chance to hit your target and every time you miss it opens your chances on being hit.
3. Always have your Blood runes on cooldown, "Blade Barrier"
4. You can never go wrong stacking stanima gems but Dodge and Defence Gems are good alltournatives
5. Use Death Stike "heals the Death Knight for an amount based on the damage done and the number of <his/her> diseases on the target."
A general rule for Tanking in a raid is to be defence caped at 540 but if you dont plan on MTing a 535 Soft cap can be acceptibale
If you plan on Main Tanking in raids in order to be effective you should be at least 20% Dodge, 17% parry and a expertice rating of 6%.
Agro
1. Taunt/ Death Grip are great agro generators.
2. Blood Boil >>>> AOE Taunt , just get a disease up on a target hit pestelance, in most cases you shoulnt lose agro with
pestelance, but for Blood Boil to be effective you need to have a infection on every target.
3. Death and Decay is a easy way to get agro but is not vary effective in generating agro.
Will be updateing through out the day