Dire Maul
For now I'm just jotting things down and will organize this better later -TacoSupreme
Maps
East Side
West Side
North Side
East Side
This is the easiest side. It has elementals and demons primarily. You get the crescent key from chasing the imp around which will open up the west and north wings.
West Side
To complete west side your main goal will be to clear all the pylons. Get to and kill the demon, then the prince. After zoning in you will see a large courtyard with giant trees patrolling. It is best to clear these first, I believe there are 8 of them. After that your goal is the pylon in the center of the courtyard. We pulled the treants on one side then the mana beings around the pylon. The abberations do a mana burn explosion when they die so mana using classes should back off to avoid that.
After clearing the first pylon head west down the staircase to kill Tendris. He does an AoE root, but nothing too difficult. Once he is dead you need to get to the area above you with all the undead. Return to the courtyard level and head into the undead area to the north. Be carefull some invisible (not stealthed) ghosts are lurking and will certainly cause some problems with adds. Untested, but warlock see invisibility could be handy here. Fight your way past the undead to the ramp inside to the north. The banshees should be a priority target because they nuke hard and silence. Once you reach the top of the ramp head east to the next pylon. After clearing it there is a pull of non-elite skeletons (aoeable, but fair ammount of hp). Head south past the skeletons to a quest NPC that will give you a quest to kill the last bosses here.
After getting the quest head south and clear another patch of skeletons. Another pylon lies right in your path, finish it as you have the others. After that pylon there is a hunter boss. She patrols close enough that you don't need to pull anything else to get her. Her multi-shot and volleys are deadly. Stay spread out and have your warrior position her so her back is to the rest of the party. If everyone is carefull and doesn't draw aggro this fight is an easy one. Her bear is sheepable (I suspect hibernate should work as well). After killing her the quickest way down is to run back to where the questgiver was and jump down to where you previously killed Tendris the giant tree.
In the NW corner of Tendris' area there is a locked door that you can open with your crescent key. Enter this hallway (watch out for the 3 invisible ghosts patrolling) and travel through it to the demon's chamber. In here your first priority is to pull the mana torrent patrols. These guys are immune to arcane, so if you want to aoe stick to fire and frost AoEs. In any case the non elites should die first as they have low hp. There are 2 pylons, you can clear them in any order you choose. One to the north and one to the south. You should only need to clear a few torrent patrols to reach them. Also just north of the hallway from Teldris is a path that takes you to library, that can be a good place to go to turn in quests if you have any and sell/repair.
Once all pylons are clear there is just the little matter of destroying Immol'thar the demon. You will proboably need to pull some of the monstrosities patrolling around his circle. The monstrosities split into 4 small demons that cast Arcane Explosion. They have about 500 hps, so can be AoEd very quickly by a mage that is prepared for them. I like to time a flamestrike to land right when the monstrosity dies then follow it up with a cone of cold to kill them all instantly. If that fails, frost nova and destroy them at range.
Now that you are at Immol'thar you need someone to be prepared to destroy the eyeball's he spawns. I covered it easily as a mage as they each have about 700hp. They spawn at a rate of 1 every 10 or seconds or so. If you use a macro to /target eye you can quickly and easily kill them. If you let them live they will cast a teleport to send people falling into the center of the circle. It is a realy bother to have your healer teleported. With the eyeballs under control he is not too difficult of a fight.
Finally the prince challenges you to face him in battle. He is in the library that seperates the north and west wings. He has a nasty knockback that can cause the warrior to lose aggro. Fighting him in a corner proboably would be a good idea. He didn't seem to impossible, especially had we known about the knockback. After he dies you can turn in that quest you received earlier that will let you come back to the library and take an item from the chest near prince.
North Side
I haven't done this yet, but have read a bit about it. Here is a copy of what quickdart had to say.
In the ogre (north) instance. There appears a tribute box after you kill the King, which you can loot and normall results in trash loot like consumables. HOWEVER. If you manage to not kill the bosses on the way to the king the tribute box will drop multiple blues which I believe do NOT drop from the normal bosses. This is why there is a quest to fix the trap (takes out one boss), and a quest to turn into an ogre (takes out another). A rogue can pick the door the first boss has the key to, and stealth loot the key the second boss guards. The drunk ogre can be bypassed in his sleep. The observer can be stunned and effectively offtanked by a rogue while the main group focuses on the king as well.
If you do this, after you kill the king, run back through and talk to the bosses you havn't killed. They will reward you with a tasty 2 hour bonus, such as 3% crit spell, 3% to crit, and 30% to attack power.
... Yes, thats 30 percent. Percent.
The ogre you trick with the disguise will also give you a quest to kill prince to get gloves. Nothing for rogues- nice for shaman/mage/priest