Similar to my raid posts looking at the role of the DPS DK in in ICC, I'll do some reviews of the heroics that most people are gearing up in for Cataclysm.
I know, some folks have moved on to raids, but I know the majority of players are still leveling and facing the challenge of heroics in their leveling blues and greens.
So, while it won't be long before epic-geared players are rofl-stomping the heroics for their random daily valor points, until then there are a few things that undergeared players need to know. I don't know if I'll do this for all the 5-mans, but I thought it might be helpful to talk about a few of them at least.
Grim Batol is a challenging 5-man in sub-359 gear. It's definitely doable, but each boss fight has several elements that make it more like a regular raid than past 5-man instances. Make a mistake, and it's easy to go from 100% to 0% very fast! Given the tuning and the raid-like mechanics, I have to say I really like this instance! In difficulty I'd put it about in the middle, somewhere between Stonecore (very DK/melee unfriendly) and Vortex Pinnacle, in which the boss fights seem quite easy (at least to me).
Instead of a separate article for each boss, I'll just put in a few comments for each boss from a DPS DK perspective.
The first boss you'll face in the instance, he can be a tricky one for inexperienced/undergeared groups. Like all of the bosses in here, there are several things that will cause damage to you, but unless they're specifically a 'death mechanic' (they'll kill you instantly if you screw up) I won't say too much about them. Umbriss is a black dragonkin. He does two things that can kill you quickly. The first is Ground Siege which does a lot of damage in a frontal area - just move behind him when he starts casting it and you'll be fine. The second is Blitz - he'll target a group member and start to cast Blitz. As long as you move to one side about 10 yards you won't get hit. The third major element to this fight is when he summons a group of troggs. (Why did it have to be Troggs?) Most of the troggs can essentially be ignored - if they get on you, merely kite them to the tank and let splash damage kill them (feel free to pestilence/death & decay). But one of the troggs will be bigger and have a purple haze around him - a Malignant Trogg. These MUST be killed away from the boss because if they die close to Umbriss they'll frenzy the boss. In addition, they do a nasty aoe blast when they die. Be careful; if your AMS is up, use it. If not, hit them with chains of ice and move away before they die. There's no reason any ranged couldn't take care of the Malignant Troggs, but it seems I've always been asked to kill them.
If you avoid the two main attacks that will kill you, and control the Troggs, this fight will go much easier.
The fight opens with a fairly quick burn on Dragha. Don't waste cds on this part, as it's pretty quick and of very little danger. The only thing to be aware of is the Invoked Fire Spirits that Dragha summons. There will be a fire patch that spawns the Spirits. The tank should kite the boss away from the patches and you should stay away until the Spirit appears. When it does, if it targets you (by a fiery line attached to you), run away! If not, hit it with a chains of ice, then run to it and kill it quickly. If it reaches it's target, people die.
After Dragha is dps'd down a bit, he calls his dragon, Valiona. When Valiona lands is a good time to pop your cooldowns. He hops on her and you'll need to continue dealing with Invoked Fire Spirits, as well as avoiding bad stuff on the ground, and staying out from in front of Valiona who does a conal flame attack to the front that can wipe you. Once Valiona is down, Dragha returns and is fairly quickly killed.
The main things to remember are quick target switches from killing the boss to the Spirits, and staying out of the fire/pools/cleave.
Throngus is a giant ettin pathing past several smaller chained ettins. Be careful clearing the trash as he can pat to your group and fighting him and his trash simultaneously is often lethal.
Open with your cds and dps away. For the first 20 sec or so it's just a tank and spank. Then Throngus will emote that he is picking a weapon. Mostly, the tanks and healers will want to be wary of what he's doing, but as a dps you'll just want to be aware of what could kill you.
If he picks a mace, the tank needs to kite him slowly around the ledge. If you pull aggro here, you'll die as his mace hits hard. Also watch the fire patches on the ground. If he picks a shield, there will be aoe damage to the group, but not too scary. If he picks two swords, the damage to the tank will be high, but it won't affect the dps too much. Be on the lookout for falling rocks/ceiling throughout the fight as the damage can add up. In a pinch, you can pop army of the dead towards the end to keep him occupied. I finished a fight from 15% after the tank died by popping army and the shammies popped earth elementals and we survived barely. As a side note, be aware that while AotD doesn't taunt raid bosses, they DO taunt every 5-man boss in Cataclysm I've used it on.
The final boss of GB is a Faceless One. Start in the middle of the room (doesn't really matter too much where), with normal dps. He does some aoe, but nothing big. When he drops a Shadow Gale focus in the room (looks like a dark whirlpool), the whole group stacks IN it to avoid dying to his Shadow Gale. As soon as the Gale is done, Erudax summons two Faceless Corrupters. They'll come from the hall you entered from. One each will head for the eggs. They need to be slowed and dps'd hard. If they're not dead when they get to the eggs, they'll start casting Umbral Mending. Try to interrupt it and/or finish them off quickly. If you don't, they'll heal the boss to full fairly fast. If your dps on the adds is fast enough, you can pop your cooldowns on the pull, otherwise save them for add phases. You should be able to kill Erudax within 2-3 Shadow Gale/add phases, but it can be done in more phases as long as you kill the Corrupters each time.
I hope that helps, and I hope you enjoy Grim Batol as much as I have!