Death Knight is the newest class and prepare for high level players. It is powerful and strength, as expected, Death Knights will be DPS/Tank Hybrids. If you can control a Death Knight, you are able to complete your wow powerleveling faster. As previously known, they will not use shields, but will rely on a high parry rating and the proper presence to mitigate damage. As known of Death Knight, it has many abilities which are able to help players gain more WoW currency and experience (WoW power leveling). As DPS, they will not do as much damage as a pure DPS class, but will bring extra flavor and utility to the table in the form of some minor crowd control, ghoul pets, and the use of diseases to deal extra damage and cause debuffs. Worldofwar.net also mentions that Tom Chilton, in his Death Knight presentation, told them that they are leaning toward letting all tank types do more DPS while tanking.

Death Knight Abilities

Presences: Much like Paladin Auras or Warrior stances, Presences will be powerful one-at-a-time self-buffs that will probably determine whether the Death Knight is taking on a Tank or DPS role in the group. Worldofwar.net reported on 3 presences, as follows:
Blood Presence will increase the Death Knight's DPS and provide a small healing effect when the Death Knight is hit.
Frost Presence will increase the Armor and Threat of the Death Knight.
Unholy Presence will provide increased attack speed and decreased global cooldown, and is being billed as the PvP presence. To use this ability in a right way would bring players more benefit including large of gold and experience.
Death Coil: It will not fear like the Warlock version, but will act like the WC3 version also used by Death Knights in that game, damaging enemies or healing friendly undead targets.
Army of the Dead: This ability will temporarily summon a small army of Undead that will fight for you. It will apparently be channeled, which makes me think it will be closer to an AE attack like a Druid's Hurricane than an actual pet ability. This ability will save your quest and combat time, it means you should take the same rewards with shorter time. It is still as the same as the power leveling wow.
Raise Dead: This will raise an actual nearby corpse, including one of a fallen ally (even in Arenas) to fight for you as a Ghoul. An ally so resurrected will have the option to control their character as a Ghoul. Ghouls will get abilities to cause diseases, stun, and fear among other things, but it seems like they will be temporary pets all the same - at least, I assume PCs will eventually be allowed to resurrect rather than stay slaves of the Death Knight.
Grip of Death: Pulls the enemy toward you and forces it to attack you (Probably a taunt effect, though It'd be great if the pulling effect works in PvP).
Blade Strike: Attacks the target and applies a disease.
Blood Strike: Deals Damage based on how many diseases are on the target.
Chains of Ice: Roots a target, then applies a snare that lifts gradually until the target regains full mobility.