One of the great hidden benefits of Niuzao's challenge is that you can pick up a Shado-Pan companion. You'll need to grab a Shado-Pan daily before you can pick up your specific choice, and depending on that day's dailies, it'll be a different group. On the day I tried, I had the warrior set, and picked Chao the Voice. If you're having trouble staying alive, you can always wait for a magic day and pick up Yalia Sagewhisper, who will be able to throw you a few extra heals. You can, of course, abandon the daily quests without completing them after you're done, you just want to pick them up long enough to get the companion.
Once you've started the battle, you have a few extra death knight toys to help you out. Of course, you'll want to keep Dark Command handy for when Deathwing turns on his son, and you should be able to Mind Freeze or Strangulate most of the Blood of the Deathborn. That said, there are going to be times you have bad timing or you just plain messed up, and a blood goes through. This is when it is helpful to be a death knight, because you can backpedal a few yards back and Death Grip Deathwing to you. Be sure you move him far enough that Wrathion steps out of the fire as well.
It's generally a good idea to save your defensive cooldowns for the missile casting elementals if you can (I ended up using Anti-Magic Shell on Reign of Fire and saving the rest for adds). When Deathwing's hitting you, you can use death strike to heal that up. There's nothing to Death Strike when the elementals are throwing missles. This is also where summoning your ghoul or even your Army of the Dead can help, because those undead will absorb missles just as well as you will. Unfortunately, you won't have a way to direct them especially, but if you angle yourself just right, you can get them to absorb a few hits, the better to allow yourself more health for when Deathwing comes back.
The Neltharion's Tears adds are best dealt with with the usual AoE method, Death and Decay and Blood Boil, with Death Strikes where needed to stay alive. I found them relatively easy to deal with, though things can get a little dodgy if they show up at the same time as a set of missle-throwing adds.
As far as talents and glyphs, you can take a few that will help you keep Wrathion alive longer. Anti-Magic Zone can help here, and if you can spare a glyph slot for Glyph of Death Coil, you can use it to shield Wrathion when you have the runic power to spare. Axphyxiate also gives you some breathing room by allowing you to stun Deathwing, which can be useful if you need to heal Wrathion or take down the adds at a crucial moment.
If you prefer to stick to the DPS fight, there are a few things to keep in mind.
The first thing is that Wrathion's Crumbling Arc, while it has a clearly visible ground effect, often damages outside that effect. Be sure you are well outside its cone. The next thing is that if Anti-Magic Shell may be a lifesaver if you can't interrupt Blood of the Deathborn.
The biggest issues I had with DPS, though, were the adds. Tears of Neltharion hit hard when you're in DPS gear, so you'll probably want to save your DPS cooldowns to take them down. Note that I did have limited success kiting them, so Chilblains plus Howling Blast might work well here, but you'll have to do it at the same time as dodging Wrathion's Crumbling Arc, so keep the circles tight and near enough to Wrathion that you can dodge out of Crumbling Arc before it hits. Wrathion's clones, on the other hand, were blessedly simple enough with Blood Boil and Howling Blast. Simply tabbing through adds with Howling Blast meant I hit the real Wrathion soon enough.
In the end, your choice of challenge may depend on your temprament. If you thrive on unpredictability, DPSing Wrathion may be your thing. If you like to have control, you may prefer to tank Deathwing. Both methods have challenges of their, but both will let you choose between the DPS or tanking cloak in the end. Personally, I'm pretty happy with choosing the tanking challenge. The story behind it was a lot cooler too.
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.