I am finding it really funny how posting a solo kill of old content as a Death knight is somehow news worthy. It looks like anything can make itself on the homepage now. There should really be somebody monitoring and approving these posts and agreeing that it should actaully be worthy other than the admin. It looks like its down to one person at the moment who is surely on the payroll.
I can bet you a lot of DKs have done exactly what this DK has done, but they have just never bothered to report or post it because they knew it was nothing special. Maybe I should go and solo a few heroics and old hardmodes on my Deathknight and then make a special video with sound effects, would that make me look pro too? I mean come on, is anybody really impressed by this? On my Deathknight I am able to outheal the healers so when you really think about it, it is not hard to do at all.
Edit 1: After reading two pages of replies, I cant help but laugh more. People seem to think Deathknights requires incredible amazing skill to play. Let me tell you the basic mechanics and how he is able to do it. It is all about Deathstrike timing which is incredibly easily to do, there is even an addon on wowhead that tells you when to use Deathstrike for the maximum healing and shield. Deathstrike is based on the last 5 seconds of damage. If you know the bosses and tactics, then you will know when to use Deathstrike. Hell, even if you dont know the bosses, the addon will tell you when to use Deathstrike anyway. The thing that is the difference between a kill and a wipe is luck. It depends on the amount of parries and dodges and other RNG factors. It would be impossible to do it every time becuase there is too much luck involved. The only skillful part (if you can call it skill) is the Deathstrike usage and cooldown usage. But any good Deathknight farming Firelands will already be an expert in this. I can guarentee most Deathknights that know the few mechanics of Deathknights will be able to do solo the same bosses as this Deathknight.