Why drop the diseases?
There's a few reasons for dropping diseases. To start with, our main defensive strike, Death Strike, no longer depends on diseases. No matter if you have one disease, two diseases, or no diseases up, Death Strike will do the same amount of damage and heal you based not on your damage dealt but your damage taken. Also, Icy Touch no longer provides an extra burst of threat when cast. Finally, disease damage in general is rather small, and with Pestilence only spreading diseases at 50 percent damage, it's even worse for AoE situations. Even beyond that, diseaseless offers some very definite advantages. You'll get earlier snap threat because you're not wasting time casting or refreshing diseases, and you'll get more healing power since you can use that frost and unholy rule to use another Death Strike.
There are some downsides to going the diseaseless route, of course. You do lose the 20 percent attack speed debuff off of Frost Fever, and your Heart Strike and Blood Boil will lose some damage and thereby will lose a little threat. Overall, though, reports from many death tanks report that any long-term threat they might lose from lack of diseases is hardly worth worrying about, since the snap threat at the beginning of the battle makes up for it. In addition, that 20 percent attack speed debuff can be taken care of by another member of the raid in many cases.
How to do it without diseases
A diseaseless build isn't actually too different from a disease-casting build. You'll want to get rid of any points you have in Epidemic, of course, and without the extra disease damage, those points in Blood-Caked Blade start looking a lot less appetizing. Crimson Scourge also loses some luster, though you will probably still want to pick it up for the 40 percent damage on Blood Boil. Otherwise, spec as normal.
For single-target fights, rune spending is pretty easy. Just alternate Death Strike and Heart Strike on the mob, with Rune Strikes when you can. On a boss, you may want to consider throwing up diseases eventually, if only because you might actually be fighting it long enough for the extra long term threat to make a difference. For multi-target attacks, you'll want to throw out Death and Decay first, followed by a quick Blood Boil, then tab through the mobs applying Death Strikes and Rune Strikes to keep your threat up until Death and Decay is ready to cast again.
Will Blizzard freeze out diseaseless tanking?
Of course, while diseaseless tanking gains traction in the community and recruits more and more devoted followers by the day, there's still that group that hangs back and offers words of caution. Diseaseless death knight builds have come and gone in the past, certainly, and every time, Blizzard has eventually made some adjustment to squelch them. This time may be no different.
One can argue, of course, that diseaseless tanking will naturally "go away" at level 81, when Outbreak gives us the option to apply diseases quickly, using no resources and only one GCD. At the same time, it does still have that 1-minute cooldown, so chances are diseaseless blood will still pretty much be diseaseless on most pulls.
If Blizzard decides to nerf diseaseless blood, Death Strike is the most likely target. The healing portion will probably be forever linked to damage taken, but if they wanted, the devs could hook the damage portion to diseases, making diseases mandatory in order to keep threat while keeping Blood Shield up as much as possible. Of course, if they want to go the non-nerf route, it's possible that they could simply buff disease damage for death knight tanks to make the actual threat garnered by casting them not insignificant. There's also the possibility of adding the threat bonus back to Icy Touch, but that might be putting too many threat tools in our arsenal, and Blizzard seems more or less dedicated to making threat something you have to work for in Cataclysm.
So there's a strong argument against getting too comfortable with diseaseless tanking, for sure. Blizzard's shown a pretty solid dedication to making sure death knights use their diseases at all times, and I wouldn't be surprised to see adjustments in game to make diseases a must-use for tanks by patch 4.0.3. We'll probably still see some of the basics of diseaseless tanking stick around and used in tandem with Outbreak, if nothing else, so it probably won't hurt too much to use for the time being. Just don't get too used to it.
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