For my talents, I used KC, How of Terror, Harvest Life, Dark Bargain, Burning Rush, and Grimoire of Supremacy.
My ilevel at the time of doing this quest was 528.
For my glyphs, I used Siphon Life, Drain Life, and Curse of Exhaustion.
I put my Demonic Gateway across the floor in the area Wrathion stands. I put my teleport midway between them off t the side.
I also used the Celestial Offering which you get from the August Celestials quartermaster.
I pre-potted, and used my Voidlord.
I stood far enough away from Wrathion to avoid his rumbles on the ground, and I just threw everything I had at him right from the beginning, including the Terrorguard (although ironically I succeeded on this quest while my Terrorguard was on CD).
As soon as the blobs appeared, I used my harvest life on them to draw them away from the voidlord because they WILL kill him quickly. I then hit the blobs with a soulburn/curse of exhaustion and ran to a gateway portal. I turned around and continued dps'ing wrathion. When the blobs were almost on me, I used the gateway, turned around, and continued dps'ing wrathion. When the blobs got to me again, if the gateway wasn't available, I used my Howl of Terror, and again continued to dps Wrathion. Also, remember to use soulburn/curse of exhaustion whenever you can to slow the blobs. During this time, I did not concentrate on killing the blobs, just slowing them and running from them while dps'ing Wrathion.
As soon as Wrathion jumps to the middle of the room and clones himself, get the heck out of Dodge! Run up to the balcony and go all the way to the back. You will take no damage from the clones up there. Use this time to bandage yourself, take a healthstone, heal your voidlord, etc.
Blobs will follow you up there, so make sure you have your voidlord follow you up to protect you. (If your voidlord dies, of course bring him back, and if you need to heal him, soulburn/healthfunnel works like a charm.) Dot up the blobs and drain life to help heal yourself up. Again, use Howl of Terror to get them away from you, along with soulburn/curse of exhaustion to slow them. Drain soul if necessary to make more shards. During this phase I DID kill the blobs so that there were none alive during the next phase. If a stray one comes up to you while the voidlord is occupying the others, then fear that one and kill it. The blobs keep coming during this phase, but they come one by one and they are manageable. If you REALLY need to get away from the blobs, use Burning Rush but use it sparingly so that you don't drain all your hard earned health away. Also, during this phase, do NOT go near Wrathion and his clones. Stay near the back of the balcony.
Eventually, Wrathion will jump up to the balcony and the entire process will start over.
Stay calm, dot up Wrathion and STAY AWAY FROM THE BLOBS. If you let the blobs attack your voidlord, your voidlord WILL die (even if you are feeding him with health funnel) and once he is dead, your death will soon follow. So, remember to drain life to take aggro off the voidlord and onto yourself, and then evade the blobs. I ran back down to the beginning area and use my demonic gateway again, and my teleport again, along with the soulburn/curse of exhaustion and the Howl of Terror. Every chance I got, I dotted up Wrathion.
I killed him after the first clone stage and before the second clone stage.
Near the end, I popped my Unending Resolve so I could take a few hits from the blobs while dps'ing Wrathion, and once Wrathion was at 10%, I went for broke and used Dark Bargain and just opened up on him and ignored the blobs.
If there are any other affliction locks who did the quest with a different strategy, please post it to help our fellow locks!