Death Knight - Best Leveling Spec
Here we go again. A new series of parses to check what's the best talent spec for leveling. This time I've done things a little differently:
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Talent spec used: Unholy lvl 61 Leveling Spec

Total: 629 DPS
Observations: Unholy is still very strong. Stronger than in the previous patch. The Death Knight's DPS alone is 517 and that's without even using Unholy Blight. This is due to the fact that Death Coil is now much stronger and easily makes up for the loss of dps from not casting Unholy Blight. This is good news because when leveling, we don't use Unholy Blight that much.
We must also remember that this was done on a single target. Unholy's DPS goes up the roof when taking on 2, 3 or 4 targets, which happens quite often when leveling, especially if you use the DK's ability to gather mobs quickly (Death's Grip and Strangulate for casters, ghoul / icy touch / death coil for the rest).
So in my opinion, Unholy is even better than before for leveling.
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- No ability with a cooldown of 1 minute or higher was used. This was to reflect more accurately a leveling situation. You don't use your cooldowns on every monster when you level up, you generally save them for elites or big fights, so that's why I didn't use them to run those tests
- Consequently, I only used the ghoul for the Unholy spec. However, I didn't use Unholy Blight, because in a real leveling situtation, you don't use it that often.
- A level 61 Death Knight with the full blue set from the starting zones was used for all 3 tests.
- The tests were done on a level 58 Servant of Sevine in the Blasted Lands and were each 10 minute long.
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Unholy
Talent spec used: Unholy lvl 61 Leveling Spec

Total: 629 DPS
Observations: Unholy is still very strong. Stronger than in the previous patch. The Death Knight's DPS alone is 517 and that's without even using Unholy Blight. This is due to the fact that Death Coil is now much stronger and easily makes up for the loss of dps from not casting Unholy Blight. This is good news because when leveling, we don't use Unholy Blight that much.
We must also remember that this was done on a single target. Unholy's DPS goes up the roof when taking on 2, 3 or 4 targets, which happens quite often when leveling, especially if you use the DK's ability to gather mobs quickly (Death's Grip and Strangulate for casters, ghoul / icy touch / death coil for the rest).
So in my opinion, Unholy is even better than before for leveling.
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Frost
____________________________________________________________________Talent spec used: Frost lvl 61 Leveling Spec

Total: 545 DPS
Observations: This is definitely better than before, the Death Knight's personal DPS is actually higher than the one of the Unholy tree, which is a first. However, with the ghoul combined it's still behind in terms of DPS. This is normal though, as frost is more and more geared towards tanking. The most significant change is the one to frost strike, it's really strong now and where it should be. Howling Blast was only used when Rime procced by the way.

Total: 545 DPS
Observations: This is definitely better than before, the Death Knight's personal DPS is actually higher than the one of the Unholy tree, which is a first. However, with the ghoul combined it's still behind in terms of DPS. This is normal though, as frost is more and more geared towards tanking. The most significant change is the one to frost strike, it's really strong now and where it should be. Howling Blast was only used when Rime procced by the way.
Blood
Talent Spec Used: Blood lvl 61 Leveling Spec

Total: 598 DPS
Observations: Blood is now pretty close to Unholy as you can see. Heart Strike is definitely worth spamming now and so is Death Coil, which is why I put one point in Morbidity at level 61.
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Conclusion
DPS Ranking
1. Unholy
2. Blood
3. Frost
Damage Taken
1. Blood - 8234
2. Frost - 14905
3. Unholy - 15209
Note: The Blood spec takes much less damage than the other two because of Blade Barrier. Frost takes less damage than Unholy thanks to Toughness.
Against Multiple Targets
1. Unholy - By far the best for AoE leveling thanks to Unholy Blight, Wandering Plague and 2 extra diseases
2. Frost - Second best thanks to Howling Blast
3. Blood - Nothing in the blood talents for extra AoE power.
Against Tough Elites
1. Unholy - Slightly better than Blood thanks to the high amount of health healed with Death Strike while 4 diseases are up. Shield of Bones and Summon Gargoyle also contribute to give it an edge.
2. Blood - Close second. +10% Parry and a large amount of life draining talents (Bloodworms, Mark of Blood, Vampiric Blood) make it very good against elites.
3. Frost - Lichborne and Unbreakable Armor help against elites, but the lack of lifedrain compared to the other two specs make it by far the weakest against tough elite mobs.
Miscelaneous
1. Unholy - One A Pale Horse simply trumps every other utility talent while leveling. +20% Mount speed, from level 57 to level 77 is a big deal.
2. Frost - Hungering Cold can be nice to get away from bad situations
3. Blood - Nothing in this department
Final Ranking
1. Unholy
2. Blood
3. Frost
Unholy is still without a doubt the best spec for leveling, followed closely by Blood. Frost is far behind, but is still a viable spec if you want to focus on tanking instances a lot while leveling.

Total: 598 DPS
Observations: Blood is now pretty close to Unholy as you can see. Heart Strike is definitely worth spamming now and so is Death Coil, which is why I put one point in Morbidity at level 61.
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Conclusion
DPS Ranking
1. Unholy
2. Blood
3. Frost
Damage Taken
1. Blood - 8234
2. Frost - 14905
3. Unholy - 15209
Note: The Blood spec takes much less damage than the other two because of Blade Barrier. Frost takes less damage than Unholy thanks to Toughness.
Against Multiple Targets
1. Unholy - By far the best for AoE leveling thanks to Unholy Blight, Wandering Plague and 2 extra diseases
2. Frost - Second best thanks to Howling Blast
3. Blood - Nothing in the blood talents for extra AoE power.
Against Tough Elites
1. Unholy - Slightly better than Blood thanks to the high amount of health healed with Death Strike while 4 diseases are up. Shield of Bones and Summon Gargoyle also contribute to give it an edge.
2. Blood - Close second. +10% Parry and a large amount of life draining talents (Bloodworms, Mark of Blood, Vampiric Blood) make it very good against elites.
3. Frost - Lichborne and Unbreakable Armor help against elites, but the lack of lifedrain compared to the other two specs make it by far the weakest against tough elite mobs.
Miscelaneous
1. Unholy - One A Pale Horse simply trumps every other utility talent while leveling. +20% Mount speed, from level 57 to level 77 is a big deal.
2. Frost - Hungering Cold can be nice to get away from bad situations
3. Blood - Nothing in this department
Final Ranking
1. Unholy
2. Blood
3. Frost
Unholy is still without a doubt the best spec for leveling, followed closely by Blood. Frost is far behind, but is still a viable spec if you want to focus on tanking instances a lot while leveling.