Death Knight Talents:

The Death Knight talent system has changes some in WoD as they added a new talent tier and some changes were also made to existing talents.

Death Knight Tier Talents:

Tier 1 (level 56)
Description
Death Coil and Frost Strike also infect your target, adding 4 sec to the duration of Frost Fever and Blood Plague, and adding an additional stack to Necrotic Plague.

Consumes your Blood Plague and Frost Fever on the target to activate up to two random fully-depleted runes as Death Runes.

30 yard range, 25 second cooldown

Surrounds the Death Knight with a vile swarm of unholy insects for 10 sec, stinging all enemies within 10 yards every 1 sec, infecting them with Blood Plague and Frost Fever. This is good for AOE fights where you want to infect a group at once or if you want to refresh diseases when outbreak is down on the main target.

90 second cooldown
Tier 2 (level 57)
Description

Draw upon unholy energy to increase Leech by 10%, and make you immune to Charm, Fear, and Sleep for 10 sec. This is a great PVP talent and is also very good self healing and protection for pve.

120 second cooldown

Places a large, stationary Anti-Magic Zone that reduces spell damage done to party or raid members inside it by 20%. The Anti-Magic Zone lasts for 3 seconds. This is usually considered the best talent in most raid encounters due to the damage it can save the raid during magic encounters. This talent had the damage reduction lowered by 20%.

2 minute cooldown

An unholy pacts grants you the ability to fight on through damage that would kill mere mortals. When you would sustain fatal damage, you instead are wrapped in a Shroud of Purgatory, absorbing incoming healing equal to the amount of damage prevented, lasting 3 sec.
If any healing absorption remains when Shroud of Purgatory expires, you die. Otherwise, you survive. This effect may only occur every 3 min.

This is a very good talent for avoiding death in tough encounters.

Tier 3 (level 58)
Description

You passively move 10% faster, and movement-impairing effects may not reduce you below 70% of normal movement speed. When activated, you gain 30% movement speed and may not be slowed below 100% of normal movement speed for 6 seconds.

This is considered to be the best PVE talent for this tier.

30 second cooldown
Victims of your Frost Fever disease are Chilled, reducing movement speed by 50% for 10 sec, and your Chains of Ice immobilizes targets for 3 sec. This is a good talent for PVP.

Lifts an enemy target off the ground and crushes their throat with dark energy, stunning them for 5 sec. Functions as a silence if the target is immune to stuns. Replaces Strangulate.

60 second cooldown. This can be a good talent for PVP.
Tier 4 (level 75)
Description
Every 15 Runic Power you spend will generate a Blood Charge. Max 12 charges. Blood Tap consumes 5 Blood Charges to activate a random fully-depleted rune as a Death Rune. This is marginally considered the best talent in this tier for blood and unholy.
When you spend Runic Power, you have a 1.50% chance per Runic Power spent to activate a random fully-depleted rune.
When you spend Runic Power, you have a 1.50% chance per Runic Power spent to increase your rune regeneration rate by 100% for 3 sec.
Tier 5 (level 60)
Description
Heals the Death Knight for 50% of max health, and absorbs incoming healing equal to 25% of max health for 15 sec. This talent is considered the strongest of this tier.
Deals [ 60.21% of AP ] Shadowfrost damage to an enemy, healing the Death Knight for 335% of damage dealt.
Converts Runic Power to health, restoring 2% of maximum health per 1 sec. Lasts until canceled or Runic Power is exhausted.
Tier 6 (level 90)
Description

Shadowy tendrils coil around all enemies within 20 yards of a target (hostile or friendly), pulling them to the target's location.

60 second cooldown

Surrounds the Death Knight with a swirling tempest of frigid air for 8 sec, chilling enemies within 8 yards every 1 sec. Each pulse reduces targets' movement speed by 15% for 3 sec, stacking up to 5 times. Upon receiving a fifth application, an enemy will be stunned for 6 sec.

60 second cooldown

Corrupts the ground in a 8 yard radius beneath the Death Knight for 10 sec. While standing in this corruption, the Death Knight is immune to effects that cause loss of control. This ability instantly removes such effects when activated. This is considered to be the best talent to have in most cases for raids and for PVP. The other 2 talents are situational

2 minute cooldown
When you land a damaging Death Coil, Frost Strike, or Rune Strike, you have a 45% chance to activate Runic Corruption, increasing your rune regeneration rate by 100% for 3 sec.
Tier 7 (level 90)
Description

A powerful disease that deals [ 1 + 2.25% of AP ] Shadowfrost damage per stack every 2 sec for 30 sec. Each time it deals damage, it gains 1 stack, and infects another nearby enemy within 8 yards if possible.
You gain 2 Runic Power whenever a target infected with Necrotic Plague attempts to attack you.
Replaces Blood Plague and Frost Fever, and is applied by any ability which applied either. This effect cannot be refreshed; it gains 1 stack instead.

Defiles the ground targeted by the Death Knight. Every 1 sec, if there are any enemies standing in the Defile, it deals (27.5% of Attack power) Shadowfrost damage to them, and grows in radius and damage by 2.5%.
Enemies standing in your Defile deal 10% less damage to you.
Replaces Death and Decay.

30 second cooldown, 1 unholy to cast, 30 yard range

Continuously deals [ 1 + AP ] Shadowfrost damage every 1 sec to enemies in a cone in front of you within 12 yards, and affects them with Mark of Sindragosa for 6 sec. Deals reduced damage to secondary targets. You will continue breathing until canceled or Runic Power is exhausted.

Mark of Sindragosa causes you to be healed for 10% of spell damage dealt by afflicted enemies.

2 minute cooldown, costs 15 runic power and 15 runic power per second.