One thing I found rather fascinating with the DK: each spec handles quite differently than the other two, even if all you’re doing is solo PvE.
Let me explain. My “for keeps” first Death Knight is now a level 62 orc. I specced him unholy, did my rounds in the starter zone, the Plaguelands and now HFP. You could say I’m starting to be quite confortable with the class’ rotations and ability timings.
I rolled a second one because I wanted to try out Blood, and later, just before the end of the newbie quests, took advantage of the free respecs to switch to frost DPS.
And one thing strikes me.
Every single spec handles differently. Oh, the basics are still here, you still apply diseases then leverage them for max damage. But the order, timings and cooldowns of each spec are vastly different, and so far, quite unique.
This was a bit unsettling at first. I expected quite some differences between unholy and the other two (ghoul pets and extended disease DoTs pretty much make that a given), but blood and frost are also very distinct. I don’t know how much this is by design, and will probably generate quite an adapting curve at each respec, but this is definitely another plus to the class.
The other thing I’m starting to see is that strict rotation thinking doesn’t really cut it. It’s more like a rough sequence of events which can be summed up like this:
- Load up diseases
- Burst with Runic Power if available
- Unleash Frost + Unholy (FU) or Blood Abilities
- Replenish own health if necessary
There’s a talent in unholy T2 which extends the duration of diseases to 18 seconds, which means DKs with this talent will have longer timespans before needing to refresh their rotations. Stuff is usually long dead before that, however, so for normal leveling mobs, the point is pretty moot.
Some things to consider pre-65 (haven’t investigated the rest, too lazy to build hour-long spreadsheets):
- Obliterate is the hardest hitting strike and uses FU runes. It is a finishing move of sorts, though, as it consumes all diseases
- For Unholy builds, Scourge Strike is your core choice until level 64 if your mob has too much health left to make an Obliterate worth it. It’s also a FU ability.
- For Blood, Heart Strike is the preferred spell until level 64, and it runs on a blood rune.
- At level 64, Blood Strike (B) outperforms Scourge and Heart Strike until their respective next ranks.
- For Frost builds, there’s a must have T3 talent, Annihilation, which makes Obliterate not consume diseases, making Obliterate the best choice. Frost Strike, while producing only 50% of Obliterate’s spreadsheet damage cannot be blocked, parried nor dodged however, which makes it a good tanking strike (duh).
Nothing exactly clearcut in the above scenarios. Now all three trees have talents which transform some runes into Death Runes (universal runes) which give more flexibility to spell sequence. In Blood, the talent in in T3, requires an Obliterate strike, and transforms Frost and Unholy into Death Runes. Both Blood and Frost builds may probably have a good synergy if they incoprorate both Annihilation (Obliterate doesn’t consume diseases) and Death Rune Mastery (transforms FU runes into Death Runes on Obliterate) into their respective builds.
Unholy’s own Death Rune talent is in T6 and uses a Blood strike to transform a Blood rune into a Death rune.
Frost’s take on this is even deeper in the tree (T7) and also uses either a Blood Strike or Pestilence to create a Death Rune.
Where does this leave us? Well, as you see, while leveling, each build is going to have different priorities. Unholy will require liberal use of blood runes to have enough unholy and frost / death runes available to sustain its diseases and use Scourge Strike.
For Blood, Obliterate will be a finishing move. After diseasing his target, Heart Strike following by RP abilities will produce a good output and a quite stable routine before having to refresh diseases. If an enemy can be finished by an Obliterate + sequence, the next fight will have death runes handy for flexibility.
Frost has to alternate between Obliterate and Blood Strike in order to maximize DPS.
Lots of things to consider. Factor in that your Disease front-loading may be resisted and you need to recast these, and contrary to my initial impression, there’s simply very little you can do in terms of clear, regular rotations. Most of the time I admit that if I’m starting to be in a cooldown bind, I still resort to pretty much random button mashing 
Looks like while Death Knights are a very powerful class while levelling, they also appear to be a rather complex class to master properly.
And I like that.
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