This means that single target fights will become a lot smoother. The ability to apply both diseases on one strike with no cool down means that your rotation isn't interrupted at all. All you do is apply a Plague Strike when you would normally apply a Scourge Strike. While Plague Strike certainly does do significantly less damage than Scourge Strike, it's not as much lost as if you had that orphaned rune hanging out there. Regarding, Festering Strike will continue to extend diseases, so in single target fights, at least, you'll still be able to use Scourge Strike to your hearts' content most of the time.
One new facet this does bring to the unholy rotation is the advantage of refreshing diseases. Diseases are a solid chunk of unholy's total damage. When you apply diseases, their damage is determined by taking a snapshot of your current stats, such as attack power. For the duration of the diseases, those modifiers stay the same, determining the exact damage and critical strike chance of each disease tick. With Plague Strike now a quick and easy way to apply diseases, death knights may find that it's worth it, in the long run, to sacrifice a Scourge Strike to use Plague Strike and refresh diseases for higher damage. This could especially prove true if you have a couple strength trinket procs up and an active strength potion. There's already some addons being worked on to help calculate this, so if this change makes it live, look for those for sure.
The greatness of Gary the gargoyle
Summon Gargoyle has long been a point of contention between the unholy death knight community and Blizzard. It's one of the only real ways unholy death knights can get an on demand burst of damage that stacks with Heroism and similar haste effects, but its strength hasn't been legendary as of late. In fact, the math suggests that if the gargoyle (dubbed Gary by the unholy community) stays how it is, there's a swiftly approaching gear point at which you'll get more DPS from spending the 60 runic power cost on Death Coil instead of the gargoyle.
Blizzard is aiming to fix this with two changes on the patch 5.2 PTR. The first is that the gargoyle costs no runic power. Given the rather low amount of damage it does and the fact it is an uncontrollable pet, which means it may not attack when and where we want, making it a "freebie" seems to be a rather fair way to bring it into equity.
That said, Blizzard did not stop there. In addition, the gargoyle will do plague damage in patch 5.2, which is a combination of nature and shadow damage. This is significant because it may mean that Gary will finally gain a benefit from Dreadblade, the unholy mastery. Mastery has strictly been a bottom barrel stat for unholy due to the fact it doesn't affect pets at all. With this change, it may see a comeback, though we may need to wait for the PTR to come up to confirm how much it benefits.
Still, this change has the effect of helping to offset two of the longest-lasting unholy complaints, lack of mastery synergy and lack of a good worthwhile burst damage button, so it's definitely a change I'll be looking forward to.
Reaping adds an Icy Touch
If the two fixes above work as well as they promise to, it may be that Unholy's AoE woes will be the last major beef the spec has. Blizzard has been making some tentative efforts to fix this. In an earlier patch, they allowed Reaping to apply to Blood Boil, essentially meaning that once you actually got your AoE rotation up, you could keep it up by allowing most of your runes to refresh over and over as death runes.
Unfortunately, this still leaves the problem of setting up the initial death runes. Currently, death knights have to plan ahead and try to use Festering Strike to set that up ahead of time. This is a sore spot for many unholy die hards, with suggestions including making unholy's Blood Boil into a frost/blood spending heavy hitter.
Blizzard didn't quite take that route, but they did add Icy Touch to Reaping. In theory, this means you could "prime" your AoE rotation by using only 2 Icy Touches, allowing you to immediately use your 2 blood runes for Blood Boil and Pestilence.
Is Unholy Fixed?
It's difficult to predict the full impact of these changes just yet, especially since the PTR isn't up, but so far, these changes are shaping up to be an excellent start to fixing unholy. Of course, recall that unholy's problem, much as with rogues, isn't the actual damage as much as the "feel" of the spec. Heading on the PTR will help us get a better grasp on whether the changes help with that aspect. Considering they promise to allow quicker burst damage and fewer orphaned runes when setting up diseases or AoE rotations, I'd say the prognosis is excellent.
As always, of course, these are PTR changes and may never make live servers, but from what we know right now, I'm hopeful they will.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.