Just gonna quickly go through some of the more notable effects of Deathwing's reawakening.
Thousand Needles Tidal Wave
First off, Thousand Needles and the tidal wave.
On top of that stone pillar is a village- we can see one building with an arc'd roof. We can assume ~5 meters for its height. The wave, comparatively, is 340 meters tall.
We will use the mass of all water in the area. Thousand Needles is oval in shape, so we will find the area of an oval (Area = Pi * r1 * r2). Using our aforementioned map, we will get a value of 565365 m for the longer radius and 173910 m for its short radius. Area is 3.089e11 m^2, multiply by 340 to get our total volume of 1.050e14 m^3. That said, it also flodded the bay- so we will get volume for that too, netting us an additional 1.022e14 m^3. Neato. Add 'em together to get 2.072e14 m^3, mass of 2.066e17 kg, moving at a speed fast enough to cover the entire area in ~10 seconds. The area is 1272.81 km long, netting us a velocity of 127281 m/s. Final KE is 1.674e27, or Multi-Continent level. As a low-end, we will assume it took ten minutes to pass through the entire area.
New m/s velocity is 2121.35 m/s, netting us a KE of 4.649e23 Joules, or Large Country level.
Shattering the Barrens
For this, we'll compare to Durotar, which is 1652.75 km long. Comparatively, the Barrens is 3838.14 km long and 1833.47 km wide. Area of an oval nets us 5.527e12 m^2. We will use the average thickness of oceanic crust as our third number (7000 m) to get a volume of 3.869e16 m^3 for our presumed tectonic plate (since the attack had effects similar to an Earthquake).
Density of oceanic crust is 3000 kg/m^3, netting us a mass of 1.161e20 kg.
Using this, 2.25 m/s is a safe speed, netting us 2.939e20 Joules, or Island level+.
Kul'Tiras Island Shifting
The tectonic plate with Kul'Tiras on it was shifted. Let's get this over with.
Kul'Tiras is about 793.19 km long and is (roughly) circular in shape, netting us an area of 4.942e11 m^2. Once again, we will use thickness of oceanic crust of 7000 m to get a volume of 3.459e15 m^3 of crust. Density is 3000 kg/m^3 for a mass of 1.038e19 kg. The plate shifted about 350 km over a relatively quick time, so one minute seems safe. 5833.33 m/s is our speed. This nets us a value of 1.766e26 Joules, or Multi-Continent level.
The Island of Kezan
Kezan was destroyed by a volcano. We'll compare the island to the Maelstrom, which is 2889.58 km wide. Comparatively, Kezan is 1762.66 km wide. It is roughly circular, so this will net us an area of 9.761e12 m^2.
The island was covered in lava, which was taller than the resident goblins, so 1.77 m for height seems fair. Total volume of lava is 1.728e13 m^3. Value for lava creation is 5000 j/cc (based on the Dark Souls calc), netting us 8.640 x 10^22 Joules, or Country level. As a high end, we could assume ten meters for height for reaching tree tops? Let's do it to be safe.
New volume is 9.761e13 m^3, netting us 4.881 x 10^23 Joules, or Large Country level. Neato.
Mists of Pandaria Dispersion
Pandaria has a width of 5000.76 km. This means the area surrounding it should have an area of 1.964e13 m^2. We can assume a height of 5000 meters if only because this mist covers all of Pandaria, including some of the more gigantic mountains, netting us an area of 9.821e16 m^3.
Vapor has a density of 0.804 kg/m^3. This makes our mass 7.896e16 kg.
To disperse it, we should assume it must not be visible from the island any more. 14 km seems fair. We actually do see the mists begin to clear somewhat during the Mists of Pandaria trailer, starting at 15:24 and the air around them is relatively clear as of 15:27. Granted, this appears to have been caused by the panda, but that isn't what happened- lore wise, Deathwing did this.
14000 m / 3 s = 4666.67 m/s.
KE = 1/2m * v^2 = 8.598 x 10^23 Joules, Large Country level.
I didn't expect such a high number but I suppose it is a continent sized area. Neat.
The Cataclysm altered several mountain chains due to tectonic activity, notably the one between the Badlands and Loch Modan. Let's calc the most notable of these.
So, according to the map, this mountain chain should be about 1408.19 km long and 217.39 wide, netting us a land area of 306126424000 m^2. We can assume average mountainous elevation (small mountains are 600 m tall) and about 37500 m average thickness of continental crust for a total volume of 1.166e16 m^3. Average density of granite is 2750 kg/m^3, netting us a value of 3.207e19 kg.
So. For a low-end, we can use speed for tectonic plates in such a scenario, 2.25 m/s, and as a reasonable high-end, assume they traveled quick enough to close the trade path instantly, crossing its radius. The trade path was about a kilometer wide, so 500 m/s.
Low-End: 8.118 x 10^19 Joules, Island level
High-End: 4.009 x 10^24 Joules, Continent level
Note that this is a feat that occurred EVERYWHERE. Tons of mountain ranges shifted as a result of this, some resulting in new zones being made.
Other Notable Feats
I'm not going to calc these, because I've made my point, but here are some other major effects of the Cataclysm that I'm pretty certain would only bolster the High 6-A rating.
- A large portion of Tanaris was completely sunk underwater
- A large portion of Gilneas was completely sunk underwater after the land itself was violently fractured
- The Greymane Wall was destroyed as a result of an earthquake
- The Wandering Isle encountered many horrible tsunamis
- Many noteworthy cities were simply destroyed flatout, including Auberdine and Feathermoon Stronghold
And so on.
Thousand Needles Gets Flooded (Low-End): 95.60 Teratons, Large Country level
Thousand Needles Gets Flooded (High-End): 400.10 Petatons, Multi-Continent level
The Barrens Gets Ruptured: 70.24 Gigatons, Island level+
Kul'Tiras is Sent Adrift: 42.21 Petatons, Multi-Continent level
Mount Kajaro Erupts on Kezan (Low-End): 20.65 Teratons, Country level
Mount Kajaro Erupts on Kezan (High-End): 116.66 Teratons, Large Country level
The Mists of Pandaria are Parted: 205.50 Teratons, Large Country level
Mountains Block Trade Paths (Low-End): 19.40 Gigatons, Island level
Mountains Block Trade Paths (High-End): 958.17 Teratons, Continent level
I might calc everything else, who knows. But for now we'll use this for the basis of Deathwing's Strength, since even one of these feats is enough for Multi-Continent.
Deathwing's Total Strength (Low-End): 42.56 Petatons, Multi-Continent level
Deathwing's Total Strength (High-End): 443.57 Petatons, Multi-Continent level