The PvP Basics
So far, for Death Knights, the biggest PvP problem can be summed up in one word: mobility. Most of a Death Knight's major damage moves require that a person be in melee range. In part, this can be fixed with a quick application of Death Grip. However, Death Grip has a somewhat restrictive cooldown (which is probably needed), and after a Death Grip, the victim is not snared or stunned, making it easy for them to run back out to range and beyond the Death Knight's reach.
Chains of Ice helps in this matter too, applying a short freeze to allow the Death Knight to catch up, then a snare which, as of this build, has been made physical, making it harder to dispel. In this case, the problem is the cost and cool down, which give more than enough chance for the target to escape simply by waiting out the Death Knight's Frost runes.
What a Death Knight really needs is a more dependable snare, one that's baseline or in the first few talent tiers, if possible. The suggestion that seems to come up the most regarding this is around the Frost talent Chilblains, which applies a 6 second snare on victims of the new Frost Fever disease. If it were converted a two-point talent and switched with Glacier Rot, a 1st tier Frost talent that mostly boosts the damage of deep Frost talented abilities, it could be easily picked up by any PvP build. There, it could provide the dependable snare that we need.
On Unholy PvP
The nice thing about Unholy as it stands is that it makes Ghouls viable in PvP and it shores up some of the primary weaknesses of a Death Knight in PvP by providing superior mobility and protection from dispelling. Consider the following Unholy/Frost PvP build.
Superior Mobility is provided from Unholy Aura and Desecration talents. Consider Desecration a bit like a reverse Frost Trap. Cast Icy Touch on a person, Death Grip them over to you, and if you can keep them in range long enough to apply Scourge Strike and follow them up with an Obliterate, you've suddenly done a while lot of damage to them and stuck them in the middle of a nice patch of ground that they'll be hard pressed to get out of. Likewise, Unholy Presence combined with Unholy Aura will give you and your teammates an even greater edge against anyone who decides to run.
If there's one complaint I have, it seems like the radius of Desecration could stand to be a little wider, or attached to me as a sort of temporary aura. But then again, that might prove a little overpowered. Still, I'd like to see it tested. In addition, I'd sort of like to see Desecrate available off of Scourge Strike as well, for those times when my Frost runes aren't ready or I really need a bit of slowing power right off the bat.
Ghouls and Guys
Ghouls, as a pet, are a little bit more disposable and hard to control than most pets. Used in PvP without supervision, they'd probably just get dragged behind a pillar and killed within seconds.
However, when you take Master of Ghouls, a whole new world is open to you. Not only are they controllable, but a leap followed by a stun or a well-timed spell interruption could end up as the different between victory and death, and this is possible only with Master of Ghouls. This alone may end up being why Unholy takes the honor of top PvP tree.
Of course, this Death Knight still think that they should just give every Ghoul a pet bar. It's not quite right that one talent can make the difference between usefulness and uselessness for a class feature. Of all our features, Ghouls to me feel the most in flux, and it'd be nice to know how central to our class they're really supposed to be. They certainly do seem central to Unholy Death Knights.
Protection and Devastation through Diseases
One thing that promises to be a weakness for Death Knights is the ability to abolish diseases. While Blood and Frost Death Knights only have 2 diseases to worry about, that in itself could be a weakness. 2 diseases are very easy for a good abolish disease to chew through. In that case, it's very nice to have not only the extra 30% resistance to dispel that Virulence brings, but also the 2 extra diseases offered by Unholy Blight and Ebon Plague. I think I'll still be watching closely to see if Death Knights do have adequate dispel protection, but the tree that's strongest in that regard is certainly Unholy.
In addition, these same diseases offer Unholy some amazing damage stacking and synergy for taking down targets. The fact that we can put down 4 diseases, and keep them up longer, means that we can get more use out of the stacking damage from Obliterate, Death Strike, and the like. Adding talents like Blood Caked Blade that give a chance to throw out something similar to a free scaling Blood Strike when they trigger only sweetens the deal. And if you need to apply some emergency crowd control, you can still wipe the slate clean with Blood Boil.
Scourge Strike is shaping up to be the crowning damage achievement in the tree. It's a straight up replacement for Plague Strike, but it relies on Shadow damage, giving the power to break through any heavily armored opponent and continue to administer pain.
In addition, the effect of Ebon Plaguebringer could very well make Unholy Death Knights very desirable members of a good caster heavy group. It's a very easy disease to apply, and makes me think that Unholy Death Knight/Affliction Warlock may be a very viable 2v2 combo come season 5, with the Death Knight adding some nice damage for the Warlock and the Warlock providing an extra level of protection for the Death Knight's diseases.
On Versatility: Unholy Grinding
With only a minimal amount of change, we switch from the above Unholy PvP build to the following Unholy grind build. By shedding a few survival and ranged attack talents, we've created a very nice pure PvE AE attack build that provides massive amounts of disease damage and plenty of area attacks.
With this, you can open with an application of Bone Shield, gather a bunch of mobs by body aggro or Death Grip, and cast Death and Decay to let it all lose. Add a Frost Fever via Icy Touch and turn on Unholy Blight, which, when it works as advertised, should do the job of applying Blood Plague for you. By then, you should probably be able to throw out a pestilence to spread the disease love around and an Obliterate to activate a nice bit of desecrated ground. If you're lucky, you'll have a few corpses to explode by then, assuming you have the spare Unholy rune or assuming the mobs aren't already dead.
There's lots of variations to this strategy, of course. You may need to Death Strike a bit to heal up, or use Lichborne or Bone Shield to prevent the need for Death Strike, or you may choose to forgo Death and Decay at first and simply use Scourge Strike and Icy Touch to get your diseases up and Pestilence to spread them, activating Unholy Blight once you have the runic power and adding Death and Decay on the next Rune cooldown.
If there's one weakness to this build, it's probably that it's very easy to become runic power starved. Unholy Blight and Gargoyle will both demand their share of runic power, and to be frank I think I'd prefer they be some flat amount of runic power with a set duration rather than constantly draining runic power. It'd also be nice to see them go down a bit in runic power cost so you could have them both out at once, since it seems a bit off that one's 51 point talent should so directly clash with the use of their 21 point talent.
I'm also honestly a bit unsure that it's so wise to put Corpse Explosion on an unholy rune, too, and would rather like to see it back on runic power. Between Bone Shield, Scourge Strike, Death and Decay, and Death Strike, I'm already rather pressed for unholy runes as it is. I'd much rather have a bit of a bump to runic power regeneration (maybe a de-nerf of Dirge) and a low Runic Power cost for Corpse Explosion, Gargoyle, and Unholy Blight.
Of course, this preview of the Unholy tree must come with the disclaimer that this is Beta, and lot will change before the whole thing goes live, especially once we all hit 80 and figure out how over or underpowered we really are. At the least, this build won't be making it intact to the live servers, as the laundry list of bugs is still growing.
Still, Unholy is looking like an amazing tree, and with a few more tweaks, it will solidify its place in my heart as my favorite tree. At the least, it's good to see that Blood isn't the only game in town.