Well, clearly it was far too fun. Unholy Blight's implementation as an aoe aura is gone. No DPS spec can afford to spend points in the utility talents like the increased run and mount speeds. And worst of all, the tree's signature strike, Scourge Strike, has been the only real story of failure for the new class.
Originally, it ignored armor, doing shadow damage instead. This was cool, but it turned out it hit too hard in PvP, and not hard enough in raids (where the target's armor was heavily debuffed, reducing the value of ignoring armor). Trying to correct this problem has led to a series of changes to the strike in almost every patch, none of those changes actually solving the problem.
The absolute low point was when, for an entire patch, Unholy DKs no longer even spent the talent point in Scourge Strike, finding it more effective DPS to contort their spec into the frost tree to focus on Obliterate as their FU* strike instead (*in this case, FU refers to the strike's cost of one frost and one unholy rune, not the developers' attitude towards unholy DKs). The devs were pretty much OK with this, and Ghostcrawler recently admitted that they only revisited SS because of player complaints. I specced out of Unholy and went for blood when this change occurred, especially in light of just how much armor penetration (useless to unholy, key for blood) was going to be on the raid gear going forward. I missed my favored spec and my trusty ghoul Beetlegobbler, but I persevered.
After that, a patch made SS marginally useful again, but not useful enough to bother with talents and glyphs that propped it up, such as Reaping and Epidemic. Hearing that Unholy was key for Anub'arak hard mode (which turned out to be true), I tried Unholy again. The disease-a-palooza was fun, but SS was still not doing too well, and armor pen still wasn't useful enough for the spec, considering how unavoidably prevalent it is on gear now. It seemed kind of sad that Unholy's viability outside of aoe situations was entirely predicated on abusing a badly-designed Glyph of Icy Touch for bonus RP to do more Death Coils, to the point that another Icy Touch was more valuable to your DPS than another Scourge Strike.
But when 3.3 hit the PTRs, a ray of hope shone on the beleaguered strike. The changes seemed genius: they fixed everything wrong with the strike while keeping its flavor. The attack would do physical damage, making armor pen attractive, but then also do a fraction of that damage on top as shadow damage. That shadow damage would be affected by talents and be able to crit independently, making many talents in Unholy attractive again. Along with the change to Glyph of Icy Touch, this brought the spec back to where I felt it was originally intended to be, and where it had been back when I fell for it: using Reaping to get more Scourge Strikes.
This change went through months of favorable testing on the PTR, without much change to it at all. Then it hits the live servers for less than two days, and already a nerf was hotfixed in.
Let's put aside the fact that other, more overpowered mechanics have been left in for months at a time.
Apparently, Unholy was doing too much damage now. I didn't really notice during our raid, given how I wasn't really paying attention to the meters with everything else going on. My first thought was that it was fine. If the dps was too high, OK, let's nerf it. They just removed the ability for the shadow portion to crit independently, I thought, how bad could that be?
Turns out: pretty fucking bad.
According to the DK math gurus over at Elitist Jerks, the change was enough that the Unholy rotation and talent spec revert to what they were before the change. The playstyle is back to being less fun and flavorful. In the end, all they have accomplished with this change is making armor penetration marginally more attractive.
Can you just get it right, guys? This is so disappointing. Once we are done with Anub Hard, I'm respeccing back to blood to get off this roller-coaster of suck.
The worst part? Ghostcrawler's post today explaining the change. Please note before reading this statement that they nerfed the ability in less than 48 hours.
"Will it stay this way for long? It's too early to tell. This implementation has a chance of working out, but we also want to see the Icecrown hard modes start up as well as the new Arena season kick in."
You read it right. They are going to leave it as-is (which is to say, broken) until they get some data from Icecrown hard modes and the new arena season (I refuse to capitalize arena, the game's greatest mistake, GC).
Those are months away.
To be clear, I'm not asking for SS or unholy, or anything about DKs, to be overpowered. I just think it's clear that Blizzard's intent is that players use SS and Reaping, but no matter how many changes they make, they just can't seem to make that appealing without breaking the game. I don't enjoy the playstyle of Unholy without those, so I'm one of the people who would like SS to be viable without being broken. And I'm quite disappointed with how badly they've done so far, and with how quick they are to break the spec while being so slow to fix it.