Shadow of Death for death knights

Shadow of Death wasn't removed for balance reasons really. It was removed because it was very hard to get working correctly. At some point when such a huge percentage of bugs are caused by one ability, it's time to take a serious look at whether or not that ability is cool enough to justify the attention it gets.

This is super rough to the point of inaccurate, but consider a matrix, where the first value is impact on the game and the second value is work involved to get it functional, bug free, and sans exploits.

Impact - Big, Work - Small = no brainer.
Impact - Big, Work - Big = painful, but worth the investment.
Impact - Small, Work - Small = eh, probably still worth the investment.
Impact - Small, Work - Big = kiss of death. :(

Now please don't infer that questioning the bang for the buck of "big work" somehow means we're lazy or cheap. (I personally qualify, but that shouldn't reflect on the team as a whole.) What I mean here is that there are a limited number of developers on the project and a limited number of hours in the day. Every hour we spend on feature X is less time spent on feature Y or else longer you have to wait to get any new features. (Yes we can also hire more people to a point, and we always are. If you're awesome, check our web page.)

Everything I said about Shadow of Death is also true of Divine Intervention. :(

A non-exhaustive list of examples of class abilities that are very hard to get working that we still support are Mind Control / Dominate Mind, Spirit of Redemption, Vanish, Blink and Heroic Leap.

Was it the fact that we weren't paying repair bills during a wipe part of it? That's pretty much the only thing I used it for, and I never had issues being rezzed afterwards :P

No, that would be a balance issue, which as I said wasn't the problem. (It is a little lame that DI became more about saving repair bills than wipe recovery, but that's a different discussion.)

The problem with DI is that we didn't have a clean way to make an encounter reset. We were increasingly having problems with the boss (especially complex encounters with lots of moving parts) not recognizing that the paladin was still alive, but invulnerable, and so the encounter was over and the boss needed to despawn and reset. It is totally a solvable problem, given enough time and resources, but we thought there were more pressing matters on the paladin and encounter side to attend to. We even tried to bring the ability back in Mists as a simpler out of combat self rez, but even that was causing so many bugs that we made the tough call to scrap the work.