While Blood is considered the redheaded stepchild of the Death Knight trees these days, a lot of in-the-know Death Knights know that it actually gets a pretty bad rap. Given a solid gear level, you can turn out some surprisingly good DPS. Take, for example, the Disease-less Blood Build. It's exactly what it sounds like: You completely skip the diseases. Use a couple Obliterates to generate Death Runes, then spam Heart Strikes and Death Coils to your heart's content. It's incredibly simple, yet it can generate some amazing DPS with a hard hitting weapon.
The con is that you need a lot of strength and a strong weapon to pull this spec off. We're talking at least a Titansteel Destroyer before you even think about it. However, once you got the gear, you're pulling even with the traditional big boy DPS specs. Plus, it avoids the traditional problems of a Blood spec with tightness -- that is, spending all of your runes before your diseases drop without wasting runic power or a Sudden Doom proc. The latter, of course, won't be as much of a problem in 3.1 since Sudden Doom will automatically trigger an extra Death Coil, but for now it is a very real problem.
As you can imagine, it's probably not appreciated that a Death Knight can churn out such high DPS while ignoring a core damage mechanic of the class, so you can expect a nerf to the idea of disease-less DPS in 3.1. While simply lowering the base damage on Heart Strike and Obliterate could work, that might penalize the disease-using Blood DPSers (Whom Blizzard recently said they want to buff) a bit too much. Luckily, that's what bonus damage is for.
In short, I'm predicting that Blood Strike, Heart Strike, and Obliterate will see a drop in their base damage to make disease-less Blood an undesirable rotation, but a bump in their bonus damage per disease so that disease-using Blood spec users aren't left in the cold. Still, until then, if you're a Death Knight DPSer with a decent weapon and at least Heroic-level gear all around, disease-less Blood is probably worth a try.
The traditional Unholy DPS build is still considered the top dog of 2-handed DPS. It also throws a monkey wrench in my idea of using bonus disease damage to readjust for disease-less Blood. Because of the third disease, adding more bonus damage to Blood Strike and Obliterate could be a recipe for disaster.
Probably what will happen here is that we'll see a major overhaul of Unholy DPS' talents. It's difficult to see Scourge Strike being nerfed too much for fear it will become weaker than obliterate, but it may be possible that crypt fever will lose a bit of potency. Ghouls continue to perform amazingly well when talented and glyphed, so it's possible that the trade off for all their new found survivability may be a damage nerf as well, or possibly a moving of the AE damage avoidance to Ravenous Dead so other specs can grab it. The other strong possibility is to make perma-ghouls baseline, thus giving all specs the chance to have an uber-buffed pet. Of course, this could lead to some serious class envy, both in PvE due to the DPS boost and in PvP due to Leap and Gnaw becoming baseline available to all specs.
Pestilence being made damageless could actually be a solid damage reducer in and of itself, or at least cause Unholy AE DPSers to give a bit more though as to how they spend their blood runes, using pestilence only at the last minute to respread diseases about to fall off, but in the end, expect some DPS nerfs, if only to make up for the rebuffing of Gargoyle.
Dual Wield DPS
32/39 Dual Wield DPS relies on dual wielding's superior scaling and the ability of Killing Machine to proc off of both weapons. Despite repeated attempts to nerf it, it seems to continue to stay on top due to superior scaling. Still, I expect 3.1 to include another attempt to cut it down to size. Funnily enough, it's possible that the reigning champion of Death Knight DPS will be getting at least one buff next patch as Unholy Blight moves to the 21point slot on the Unholy tree. The loss of Gargoyle may seem like a blow at first, but being able to have that nearly constant Unholy Blight damage going alongside Howling Blast will likely more than make up for it.
That said, Blizzard's shuffling of the Frost tree is probably what will throw a monkey wrench into the works here. I expect that Killing Machine and Necrosis will be bumped further down their trees, such that a dual wielder will essentially be forced to pick one or the other. Separating the cornerstones of a dual wield build may be the only real way to actually get back to down to level with 2-handed DPS.
Of course, the other problem is not making dual wield damage completely obsolete. In that case, the solution may involve tweaking Killing Machine yet again. The problem here is that any viable criticism or ideas from us on how to properly bring 32/39 down to earth may have to wait until we see exactly what happens to the frost tree. At the least, I'm still expecting Glacier Rot and Black Ice to move deep enough down the tree in order to give Unholy and Blood a reason to take a second look at the early frost tree.
The waiting is the hardest part
It seems likely we'll know for sure how everything is going down in the next few days, and we'll have a lot to talk about then. In the end, we probably have a few more months on live to play with these builds to our hearts content, and enough time on the PTR to whip up some replacements for 3.1. Either way, though, I'd advise everyone to strap in and sit tight. Regardless of how things shake out, it's probably going to be a bumpy ride, and things will change by the time we're on the other side, perhaps drastically. We'll keep you posted.