Baradin Hold
This is the Cataclysm equivelant to VoA from the Wrath expansion - a raid instance that can only be accessed after a faction win in Tol Barad. Currently there is only one boss available in this raid instance, however, more will be unlocked over time.
Argaloth
The Argaloth fight is pretty simple. There are two phases to the fight. The first phase is a spank-and-tank with the raid divided into two groups. The second phase is a "don't stand in fire" dynamic, with the entire raid running around to avoid standing in fire.
In the first phase, split your raid into two groups. One group is in front, one group is in back. This is because Argaloth hits with an ability called Meteor Strike, which does an immense amount of damage. That damage is spread evenly among anyone stacked on top of the target. So each group stacks on top of its tank, helping to mitigate Meteor Strike's immense damage by taking a small portion.
At the same time, Meteor Strike leaves a debuff behind that means your tank will take even more damage -- that's why you have two groups. Each time the strike happens, have the other tank taunt the boss. That will give the afflicted tank time to have the debuff drop, so they can take the boss back.
Consuming Darkness is a DoT that will absolutely kill its target. There's no help for it but to cleanse it.
Argaloth will enter his other phase when he reaches 66% and 33% of his life. This phases involves Fel Firestorm, an aura Argaloth applies to himself for 15 seconds. During this time, Fel Firestorm will spawn fire under the ground of raid members, forcing them to move nearly nonstop. It's important to note that DPS with instants should "Keep attacking, raiders!" during Fel Firestorm. After the ability is over, Argaloth returns to his normal phase.
Argaloth has a 5 minute enrage timer. In 5 minutes, if he's not dead, Argaloth gets super angry and one-shots each tank, then every one else in the raid one at a time. On average, your raid should be putting out at least 10,000 damage per second for each raid damage dealer. Most groups do the fight with two tanks and two healers in 10-man, with twice the healing in 25-man.
Occu'thar
Before you engage the trash, make sure your whole raid is present and accounted for and ready to move as one group. Your entire raid group should stack on one tank, and then stand together for the pull. This is because the Eyes will each focus on different raid members and cast Gaze of Occu'thar, a minor-damage DOT that explodes for huge damage after 10 seconds. Due to this, you want to stack up and AOE them down before 10 seconds pass. Other than this, the Eyes of Occu'thar do nothing special.
Occu'thar
Following Baradin Hold/ Vault of Archavon tradition, Occu'thar is a boss of few mechanics and should provide little challenge to a well-geared and competent raid group. He has 23.7 million hit points on 10-man difficulty and 71 million on 25-man. With his 5-minute enrage timer, you should expect your DPS on 10-man to average around 15,000 DPS, with 25-man having a slightly more forgiving DPS requirement of around 14,000 per person. For 10-man, my group killed it with two tanks, three healers, and five DPS, though two good healers should suffice. For 25-man, we used two tanks, six healers, and 17 DPS, but those numbers are also not required.
Searing Shadows
Occu'thar's first main ability is called Searing Shadows. Searing Shadows is the reason you need two tanks for this encounter. A 2.5-second cast, Searing Shadows hits everyone in a frontal cone for massive shadow damage, and then increases their shadow damage taken by 100% for 30 seconds. Due to this, your off tank will taunt as soon as the main tank receives Searing Shadows, and then the main tank will taunt back once the off tank gets debuffed. This continues until Occu'thar is dead.
Unlike Argaloth's Meteor Slash, this ability does not share damage between everyone hit by it, meaning no one but your tanks should take Searing Shadows. As Searing Shadows hits everyone in a 60-degree frontal cone, you'll want one tank to stand with his back toward the back left corner of the room and the other tank to stand with his back to the back right corner. Once positioning and taunts are figured out, Searing Shadows is an easy mechanic.
Focused Fire
The second ability Occu'thar uses is Focused Fire. In true wannabe-Beholder style, Occu'thar will turn around and fire giant eyebeams of death at a random player. This leaves a huge and very visible patch of pink energy on the ground, which will tick for large amounts of fire damage every 1 second for 12 seconds.
Due to Focused Fire's 12-yard radius, you should make it a point to try to stay 12 yards away from the nearest ally. You generally will want your healers to take the center of the room, while ranged DPS will fan out to the left and right. On 10-man, it's very simple to have Focused Fire casts that hit only one person.
The Eyes of Occu'thar
If you've survived the trash leading up to Occu'thar, you're already prepared to deal with his third and last mechanic: the Eyes of Occu'thar. Approximately once per minute, Occu'thar will summon Eyes of Occu'thar for every member of the raid. Just like the trash at the beginning of the instance, they will cast Gaze of Occu'thar on their chosen raid member to deal minor DOT damage for 10 seconds. At the end of that 10 seconds, those Eyes left alive will explode for around 25,000 damage to every raider.
As soon as the Eyes come up, you want to collapse to a predetermined spot and start a hard AOE burn phase. These little nuisances don't have a lot of hit points, so provided you stack well and have players who know how to AOE, this phase should be a piece of cake. Because everyone in the raid is being hit by the minor shadow damage DOT and there's a chance for a few Eye explosions, healers might want to use raid cooldowns like Power Word: Barrier or Spirit Link Totem near the end of the AOE phase.
The last thing to remember about the Eyes of Occu'thar phase is that it will always be immediately followed by a Focused Fire. Since everyone is stacked in the add phase, it's of absolute importance to be ready to spread to your original positions as soon as the add phase ends. Personal cooldowns should be used to mitigate incoming damage, and this is probably the optimal time for resto druids to blow their Tranquility. This transition from Eyes to Focused Fire will be the most healing-intense part of the fight, and if you can get through it easily, there's no reason you cannot down the encounter.