Essence of Order

I thought I'd give out a few tips on how I got through this fight as a Destruction Warlock.
First off I'd like to mention that I had a fairly low ilvl (479) and that I am not very experienced in a raiding atmosphere or even heroics for that matter- basically I would never brag about my skill level, to be clear.

Talents I chose/used and why:
15- [spell=108370] the absorption all but renders his damage easy to deal with, provided you do not stand in his [spell=134235] which you will know when it is coming, all you need to do his side step a few feet to one direction

30- [spell=30283] I simply designated this as one of my 3 ohcrap buttons. When he is casting [spell=134225] you absolutely must interrupt it as you'll likely not be able to get away from it

45- [spell=108416] Another ohcrap button should you for some reason be unable to interrupt [spell=134225]

60- [spell=108482] I took this as it will be useful in the Kanrethad fight, and neither of the other two options brought anything to the table with the strategy I used on this fight

75- [spell=108503] This is the talent that really saved me. I read a lot (LOT) of other guides that recommended letting the Voidwalker/lord tank him, however, I found that sacking my Felhunter and using my Command Demon button to use the Felhunter's [spell=103135] all but knocked the [spell=134225] spell off my worry list (if for some reason you don't have time, or whatever- see any of my ohcrap tools.

90- [spell=108508] I actually found this more useful than [spell=137587] for one reason alone: the moment you see one of his adds coming into the picture hit [spell=108683] followed by [spell=348] and you can ensure that all adds will get hit (more on the significance of this below).

On to Glyphs:
[spell=56218] this works best when your Immolate hits more targets and hitting every add that comes through Fire and Brimstone will help keep your health pool in a manageable range.

[spell=56224] Using our Healthstone as heal over time combined with the constant stream of heals coming in from FnB+Immolate supplemented my health pool nicely.

As far as specific strategies are concerned after the above setups were made:
Since you won't be using a demon don't worry about Curse of Elements, dust off your Curse of Enfeeblement to help lessen the damage you'll be taking throughout the fight. Simply follow your single target priorities on the main target while switching to a simple AoE rotation when the adds come in= [spell=108683] then [spell=348] and keep [spell=5740] going. [spell=108508] will also make sure that RoF keeps hitting the adds (generating embers) as this IS a movement heavy encounter.

I think I only casted Chaos Bolt once or twice, the rest of the time Embers were only used for [spell=108683] and [spell=114635] when my health got low (occasionally I needed to spam this, your results may vary). Once his health was low enough (a million or so hp's ?) I spammed [spell=17877] and took him down.

I hope this helps out any fellow locks who are having fits on this fight, and if anyone smarter than myself wants to use the content of this strategy to put it into a cleaner, more easy to read 'guide' by all means feel free.

I got this from a video:

How to do it as Destro:

Let your voidwalker tank it..

Be constantly on the move to avoid Spellfire.

Try to get Kil'jaeden's cunning as your 90 talent, this will allow you to cast on the move.

The adds:

I died 3 times on these, the trick is: They. don't. die.

Actually they DO die, but new ones spawn so fast it has no point, the key is to use them to generate burning Embers.

The trick is to use Rain of Fire on them constantly, this way you generate Burning embers like crazy.

Use Ember Tap to heal yourself, even spam the heal if necessary.

If your voidwalker dies, use Flames of Xoroth, then let the voidwalker aggro the boss again and just use Soulshatter or Demonic Gateway if necessary to lose aggro.

Don't forget to use Shadowfury to stun the boss when he begins to cast Hellfire, the cooldowns are about the same so when Hellfire is cast again you should be able to use Shadowfury again.

Did it this way as Destro at item level 432.

How to defeat as a mediocre Affliction lock:

Ensure you have the talents Harvest Life and Shadowfury. I also had Dark bargain, Burning Rush, GoSup, Kiljaeden's Cunning.

I also had someone sitting next to me at my computer calling out attacks and when the red orbs (souls) were incoming. Probably not needed if you are a better player than I.

Let your Void lord tank. Stick with your standard Curse of Elements, Haunt, and DoT rotations. When spellflame comes up, just move hair to the right. Keep moving around the boss in this manner (his fire will end up looking like spokes of a wheel with him in the center, but dissapears by the time you've gone all the way around).

HELLFIRE MUST BE INTERRUPTED.

When the souls come, get in close to the boss, throw a SB+Seed of Corruption on him, and then Harvest Life. You'll never have to target a Rain of Fire or untarget the boss. The combination of the attacks will heal you up a bit and kill the adds at the same time.

You can also SB+Health Funnel your Void Lord as needed, or just save a stone to instant resummon. Either work.

Good luck!