Not much changes mechanically from Normal to Hard modes. The main differences are:
- The bosses hit much harder
- There are strict time limits before the next boss/set of bosses emerge
- There is no speed boost to get out of the way of Icehowl's charge
- Icehowl's enrage cannot be removed by Tranquilizing Shot
Vigilant runs a 3 Tank, 6 healer, 16 DPS setup (with about an even number of ranged and melee, sometimes a little melee heavy). This allows for minimal Impales on tanks, no need for a ranged (and somewhat squishy) tank for the Jormungar, and gives us a bit of a buffer should one of the tanks take a bad hit. The downside of this is sacrificing a DPS spot, and with the stringent timers for the entrance of the next boss phase and the final enrage, everyone needs to live and dish out as much damage as possible.
Gormokk the Impaler
For the first boss, we arrange the raid so he is tanked parallel to the boss entrance doors, with the tank on the left and the melee behind the boss on the right. Ranged and healers spread out around the boss in a semi-circle, not standing too close to one another. This is to prevent Fire Bombs from landing on too many people at once.
A good idea is to angle your camera up so that you can see above Gormokk, and watch the bomb trajectory in the air. Though sometimes difficult with needing to also keep track of debuffs, health pools and snobolds, if you can manage to see it you can often avoid the patch of fire all together.
Your tanks should be on a rotation, calling out when they are taunting off of each other. They should also be using cooldowns regularly towards the end (as Gormokk will have more stacks of Rising Anger), and calling out to the healers with cooldowns to use them. They will want to taunt at 2-3 stacks of impale, and waiting (hopefully) until their stacks fall off to taunt again.
When Snobolds go out, it is a time to prioritize. If the snobold lands on a ranged or a healer, that person needs to immediately move into the melee. This will allow it to be cleaved. All DPS who can quickly ramp up DPS should switch to this snobold to remove it, while those who cannot (such as a Feral Druid who would have to build up bleeds) should simply try to cleave it. Ranged DPS should switch as well, especially if it is a snobold on a healer or tank. Snobolds on tanks must also be DPS'd off quickly to reduce their chance of being stunned and killed.
Snobolds on melee DPS, however, can be ignored for the time being. They do not present a serious threat and are not worth the DPS sacrifice on the boss. They will be cleaned up either near Gormokk's death (in the case of having a good head start on the Jormungar timer) or during transitions and submerges.
Acidmaw and Dreadscale
After 2 minutes and 20 seconds, Acidmaw and Dreadscale will be announced, and ten seconds after this, Dreadscale will strike. Gormokk needs to be dead by this point. Immediately, everyone should move away from the door. It's possible for a Jormungar to go for a squishy melee DPS right off the bat, and if they die without the Jormungar being damaged or gaining threat from anyone else, they will despawn, wasting your attempt. It's also a good idea to use Hand of Protection on the tank with the most Impales (or the longest duration remaining), immediately followed by Hand of Freedom to remove the Hand of Protection.
You will have a grounded worm and a mobile worm, and throughout the fight their positions and status (grounded or mobile) will switch. You should always have two tanks on the mobile worm and one on the grounded worm. However, on the mobile worm, only one tank should be in front of the boss at any time, and no DPS, healer or other tank should stand in front of the worm. The mobile worm should be moved in a circle around the outside of the room, only being moved after it drops a cloud of poison (to reduce poison spread over the whole room).
Whenever the first tank gains the debuff (be it Burning Bile or Paralytic Poison), the other tank should taunt the boss. However, the second tank should only taunt after the first tank has been hit by the worm's spewing attack. If the second tank taunts off prior, the first tank will remain the target of the spew and the Jormungar will turn to face that tank to use its attack, hitting everyone that tank is near and likely causing a wipe.
You may notice there's no map for this fight, but that is due to its highly mobile nature and the Jormungar's ever-changing positions. There are some keys to remember, however. Everyone should spread out. This will reduce the chance of a mass of people being debuffed with Burning Bile or Paralytic Poison. Healers have priority of position. If a healer is near you and you are a DPS, move away from them. They need to be able to reach the tanks and/or raid to keep them alive. Their targets may often be on two different sides of the room, while you will only have one target to position around.
Unless you are trying for the achievement, Acidmaw should die first. According to personal preference, you can blow Heroism/Bloodlust as soon as your tank has a nice hold on threat to burn him down. When attacking any grounded worm, your melee should be able to self-divide into groups to minimize possible spreading of Paralytic Poison (and, later, prevent Burning Bile explosions that decimate half your attack force). They should also check behind themselves to ensure they are not going to be launched into patches of poison when the grounded worm whirls around.
Managing debuffs is important in this phase. People with Burning Bile need to seek out people with Paralytic Poison to burn off the debuff, without damaging people in the raid too much and without standing next to each other (blowing each other up for multiple sources of damage). When Acidmaw is dead, everyone with Burning Bile's only job is to stay away from other people (and, if you're a healer, keep healing, or a ranged DPS, keep DPSing). You can very easily cause a wipe by blowing up other people in the raid, so just be safe.
When Acidmaw is dead, all DPS should (obviously) switch to Dreadscale. Dreadscale will enrage, so it's important to make sure adequate healing is on the tank. Keep performing as you did when Acidmaw was alive, and you should have your kill. Make sure to monitor your timers; Dreadmaw should be dead or near-dead by the time Icehowl arrives.
Three minutes after the beginning of the worm fight, Icehowl will emerge. A tank needs to pick him up immediately and bring him to the center as soon as possible. Your raid needs to then arrange yourselves around him in a circle, as spread out as possible (including melee; use the sides and back).
This is important for two reasons: to prevent a large portion of the raid from being hit with the Arctic Breath, and to prevent stacking when Icehowl uses Massive Crash to knock people into the walls (and perhaps making them unable to see through someone else's character model). Healers should be spread out evenly to be able to cover people caught in Breath.
It is important, while arranging yourself, to look behind you. Will you be knocked into the few patches of lingering poison? Are you going to be knocked into a doorway (boss entrance doorway is okay, smaller doorways are not)? Are there a lot of people around you? Move. Make sure wherever you are is well-positioned both for your role and for boss mechanics. Remember, you have no speed boost and no recovery from an enrage. While it is possible one tank may survive the enrage through stacking cooldowns, it is also very likely you will be down many DPS from the Whirl or random threat before his enrage wears off.
Something else important to note is not to charge into Icehowl too early while he is running at the wall. Even if he seems to have hit the wall, wait a moment before charging in, as you may get caught in front of him, causing an enrage. This happened to one of our Feral Druids and, while not his fault (other raid members confirmed that his charge had been immediately after Icehowl had hit the wall), it is better to be safe than sorry. If you still have Heroism/Bloodlust, when he is stunned and against the wall is the time to pop it. When he comes up, resume your positions, rinse and repeat, and you should have a dead Icehowl.