After a most enjoyable if not a little long guild Naxx run Monday I was able to collect enough gear to hit and defense cap my death knight after dropping a chunk of change yesterday.
Speaking of the Naxx run, it was your run of the mill to the point where we cleared all 4 wings within raid time. Our interim leadership was ready to call it a night, but by popular demand we figured we'd give the last two bosses a shot. After all we had one shotted everything so far. So we got the boney dragon down in one try and moved on to KT, wiped once at a ridiculous 5% or something. I'm sure I was not the only one that had zero expectations and was amazed that we got that far. Two brand new to naxx players, 6 melee and only one ranged DPS. Second attempt we got him down nice and clean. 3 people get the Naxx clear achievement, yay!
So back to the death knight tanking. From a bear's perspective there is a whole lot more to watch and think about as a death knight. The worst thing that can happen to a bear is to find yourself without rage and have to fight for threat without it. The death knight equivalent is to be without runes or runic power when you need it which can happen at any time in a fight where as a bear will generally only have a rage issue early on.
So as a death knight you have to think ahead, "Some adds will come out soon, I need to have my death and decay ready." and/or "Let me make sure I have a blood rune available to refresh my diseases on everything." This is in stark contrast to what goes through the mind of a bear, "Hey... adds! Swipe."
While bears just go about spamming buttons, death knights have a more structured approach that isn't as flexible with a mistake or two. For example you pull a group, burn all your runes building initial threat and woops where that other group come from. Death and decay will take too long, blood boil won't help much without diseases with everyone AOEing them. You have to spread diseases and then blood boil them preferably before they eat anyone. For a bear there is no change of tactics, swipe, swipe.
Another thing about death knights, specifically the blood spec I play is that you have to balance resources between threat and mitigation. I have a lot of oh shit buttons that require a blood rune and the cooldown associated with them. In a pinch I might have to stop generating aggro to keep myself alive. I'm sure this will be less and less of a problem as I gear up, but it is another thing you never have to think about as a bear.
I don't have and experience with warriors or paladins, but from what I know of their abilities death knights are a step above them in complexity as well. Warriors do have a comparable number of tricks up their sleeves, but again near infinite resources to work with most of the time. That whole can't do something exactly when you want to is something unique to the death knight play style.
Death knights have the ability to really shine when used to their full potential though. I tanked heroic Halls of Lightning yesterday and after forgetting frost presence, then tanking gear for the first couple pulls things went pretty smoothly. That frost presence thing is easy to miss at times, I need a big furry reminder in the center of my screen. And tanking in dps gear isn't so terrible for a feral druid. Just a couple more things that death knights need to be more aware of.
So about death knight awesomeness, we crashed and burned the first Loken attempt; healer went down in a nova and I was left to fend for myself. I completely forgot to use two of my abilities, one of which was my anti magic shell the other was another healing ability. Least I remembered to pop lichborne and heal myself with a few death coils. In any case the second attempt I am pretty sure I kept healed all by myself although with druid hots flying around one can never be entirely sure.