Well, it’s dead, so here’s how you kill it!  Full text version below.

Hello and welcome to MMOScholar’s 25man Heroic Ragnaros Guide. This guide assumes you already know the normal mode of the encounter so I’ll only cover the hardmode mechanics in this guide.

In Phase 1 Magma traps now place a 45 second debuff on all players when blown up. This debuff causes any further explosions to do 50% more damage to the raid, guaranteeing a wipe. This means that during Phase 1 you’ll typically have 2 Magma Traps still up going into the transition and players will need to take extra care to make sure they’re not knocked into Magma traps by Wrath of Ragnaros during the phase.
Lava walls continue as normal in this phase, as well as the melee Knockback.

The transition phases differ from normal in that the spawn points of Sons of Flame are not set. He will still hammer in one of the three set locations, but the Sons can spawn anywhere on either side of the hammer. Most times you’ll see decently even splits, but others you’ll find 8 on one side or 6 right next to the hammer. Having assigned stuns and knockbacks plays an extremely key role in this phase of the encounter. The damage in this phase is also far from inconsequential.

    Phase 2

In phase 2 there are 2 new mechanics. When Molten Elementals are within 6 yards of each other, they gain the Molten Power buff which increases their damage by 25% per elemental in range as well as making them unsnarable, rootable, or stunnable. This means that if you used the traditional method of stacking and tanking them, each add would be melee’ing for about a million damage.

To counter this mechanic we make a tight stack towards the middle of the room. As seeds are spawning, we stampeding roar and move as a group towards a side, avoiding the initial seed damage, but making sure the Molten Elementals are tightly clumped for our AoE. Boomkins, Frost DK’s, and Hunters are extremely good for this phase of the fight, but every person who can contribute to AoE without being melee’d, should contribute.

If your raid comp is lacking in AoE DPS, you can send players with melee range AoE’s a bit further out from the camp and let them run back into melee to AoE with abilities such as Hellfire or Arcane Explosion, then just cleaving their adds down after the initial set is down. We utilize Rallying Cry, Aura Mastery, and Power Word: Barrier to handle the seed explosion damage.

Shortly after each set of Molten seeds, Rag will cast World in Flames. The World in Flames mechanic is similar to the normal mechanic, Engulfing Flames, except he casts it three or four times in succession. World in Flames can not target the same area of the room twice in a row so moving into an area that was just previously engulfed will always be safe. Lava Waves will continue as normal right after the dancing.

Once the boss hits 40% you want to really push damage before he submerges to help make the phase 3 DPS check when he re-emerges.
In the second transition you’re confronted with 2 Lava Scions. We handle adds as usual except leaving one marked add up as long as possible, usually the one furthest from the hammer. This allows us to maximize Lava Scion damage so that we have less spread damage to do and can effectively meet the ridiculous phase 3 DPS check. Combat rogues are ideal for taking out Lava Scions quickly and easily, especially since they can continue to blade flurry off of them and finish them off once phase 3 begins.

Phase 3

Phase 3 is an all out DPS burn. Your goal is to make it to Phase 4 with only 2 meteors alive, which requires quite an extensive amount of DPS. Minimizing movement for your raid is key here and bringing execute classes, such as Warriors and Warlocks helps exponentially. We split the raid onto opposite sides of the room and have healing priests on either side knocking meteors back into the lava. The goal with each meteor is to make sure your DPS don’t have to move or waste their own DPS on them.

Once knocked back, ideally they target a raid member on the opposite side of where the meteor was just knocked back. This gives ample time with the meteor running through the lava with no one’s DPS being disturbed.

On top of the meteors in this phase, World in Flames will continue to be cast in relatively quick intervals.

Phase 4

Once the boss reaches 10%, he will submerge, the meteors will be frozen by your 3 new druid friends, and the final phase of the encounter begins.
Phase 4 is where the Heroic Encounter really just begins. There are a very large number of mechanics at work in Phase 4 all of which are extremely important to know inside and out. At the beginning of the phase your 2 meteors will still be active from the last phase, fixating players as usual. We knockback the meteors nonstop, as soon as possible, for the first set.

The 2 biggest mechanics early on in this phase are Magma Geyser and Breadth of Frost. If at any point more than 9 players are within 6 yards of each other a Magma Geyser will spout from the ground. This is especially important when Breadth of Frost spawns are out. Shortly after the phase begins a Breadth of Frost will spawn in a random place in the room. Breadth of Frost’s effects make you immune to Superheated Stacks and damage if you’re standing in it. We stack on 3 marks in a triangle inside of the breadth of frost. It’s important that when you run into or out of your mark area, you do not run through or near any other groups, as it will cause a geyser to spawn and destroy your frost patch.

Let’s get back to the meteors. Once our 2nd Breadth of Frost has spawned, we kite one of our 2 meteors into the Breadth we were all standing in. Once the meteors reach a Breadth of Frost, they take 15000% bonus damage. This really means that they take about normal damage and require 3.3mil damage to go into them in 10 seconds to kill them before they unfreeze and take 1% damage again.

We then move to our 2nd Breadth of Frost and repeat what we just did. When needed, fixated players must kite the meteors away from the group until they can be knocked back safely or you are going to kill the 2nd one with your 2nd frost patch.

During this phase Ragnaros will periodically cast Empowered Sulfuras. When this ability is used your tanks must kite Ragnaros into an Entangling Root trap. This root lasts 10 seconds and is enough time for the effect to wear off of Ragnaros. If your tank is melee’d while this ability is active, it is an instant raid wipe.
The final mechanic is the one that ends up being the most important, Dreadflame. 5 seconds after your first Breadth spawns one of your druid companions will spawn a Cloudburst. Cloudburst allows 3 players to be immune to superheated and Dreadflame damage, as well as allowing them to clear Dreadflame by walking over it to extinguish it.

Once Dreadflame is on the ground it will multiply itself every few seconds. If it’s not taken care of extremely quickly it can grow to be unmanageable. As the fight continues, dreadflame spawns speed up to the point where it is impossible to clear all of the fire on the ground. At this point your cloudburst soakers should move in towards the raid and focus more on protecting the raid from incoming fire, rather than attempting to clear everything out there.

Once both meteors are dead the fight becomes a straight DPS check in a race against the dreadflame soft enrage. Once the boss reaches 15% you ideally want to move to the newest frost patch and have your Cloudburst soakers stack, one on each mark. This allows you to not have to move for dreadflame in the camps, as it will overrun you if you continue to attempt to soak it.

With your entire raid DPS’ing at this point you should be able to burn the boss before the frost patch despawns, however, raid cooldowns can be chained for a bit after the patch has despawned if absolutely necessary.