Relevant Talents used:

Talents doesn't really matter too much on this fight as no talent is a clear superior choice. But the ones I used are:

Body and Soul
Solace and Insanity
Desperate Prayer
Twist of Fate
Divine Star

iLvl: 525

Overall not too tight in terms of DPS requirements, but there are a couple of checkpoints or mechanics within the fight that requires a DPS check. There isn't much healing required due to low damage taken so the fight is mostly about the DPS. The fight basically has 2 phases. The first phase involves killing Deathwing's tentacle on each platform and this can be done in any order. Each platform involves basically doing the same things: Kill a Mutated Corruption, an Elementium Bolt, AoE some bloods, and finally kill the Arm/Wing Tentacle. There is usually a preferred order however, since each time you finish with one platform, you will lose one of the buffs that you get from the aspects at the start of the fight. Hence the preferred order usually means losing the most insignificant buff first. With that said, I personally went with Ysera's platform first, followed by Alexstrasza, Nozdormu, and finally Kalecgos.

Dealing with Mutated Corruptions:
Start DPSing Mutated Corruption as soon as it comes out, if there isn't anyone in its melee range, it will start to attack the aspects (in this case Ysera). If the aspect's health reaches zero, the encounter will reset. Fortunately they can take quite a beating and if the Mutated Corruption can be killed quickly enough, there is no need to stand in melee range. I personally stood in melee for a couple of hits just in case. The main mechanic to watch out for is Impale. This will deal 200k+ damage and places a debuff that increases the next Impale damage taken by 100%. Usually the corruption will die before the second Impale comes out, but if it doesn't, use Dispersion to tank the second Impale.

Elementium Bolt:
Deathwing summons an Elementium bolt that will land on the platform. To minimize damage, stand far away from the point of impact. Upon landing it will pulse raid-wide AoE damage so preferably kill it before it lands. However since Mutated Corruption has a higher kill priority, usually the bolt doesn't get killed until after it lands.

Dealing with Hemorrhage:
Deathwing will summon a group of Regenerative Bloods that will heal to full health once they reach max energy. They should go down with Mind Sear plus T6 talent before they regenerate. If any does slip through and regenerate, single target them down. They can stack a nasty dot, but save all healing/shields until after all of them are down. Do make sure that the Mutated Corruption is down before these bloods spawn. I am unsure if Nozdormu's Time Zone (that yellow bubbled area that looks like a PW:B) will slow their rate of regeneration though. On the final platform, you will not have the 20% haste buff which Nozdormu provides, so killing the bloods quickly becomes one of the DPS checks I mentioned earlier.

Blistering Tentacles:
When an arm/wing tentacle reaches 75%, 50%, and 25%, Blistering tentacles will sprout from the main tentacle. For most of the encounter, Alexstrasza will kill them for you, but once you lose her buff they must be single targeted down.

Cataclysm:
The final mechanic to deal with on each platform. This is not really a mechanic. But once Deathwing starts casting this, you will have 1 minute to finish off the Arm/Wing Tentacle which is usually more than enough, given that you will get a 100% increase to damage while he is casting this. Once the tentacle is down, move onto the next platform.

Phase 2:
The first set of Elementium Fragments should be killed, while using a defensive (such as dispersion or Dream) for their Shrapnels. The two Elementium Terrors that follows applies a nasty stacking dot which means if they are not down in 15 seconds you are dead and yes in my kill video, I actually underestimated this debuff. It is recommended to save both Shadowfiend and Vampiric Embrace for this. If you have not used Dream to deal with Shrapnels earlier, then use it when Vampiric Embrace is about to expire as a safe measure. Also stay in the time zone to slow down the rate of the debuff stacking (I have no idea why I moved out of it, I guess I was expecting the shadowfiend to get 2 shotted so I tried to move away from the other one as far as possible). Killing these two adds quickly is another DPS check mechanic. You will not have both Shadowfiend AND VE ready for the next pair of Elementium Terrors so you should aim to finish off Deathwing before they spawn (ignore the second set of Elementium Fragments). This is the final DPS check for the fight.