This quest requires that you kill the Emperor, but do NOT kill the Princess. Once the Emperor is dead, she will become friendly and you can talk to her to complete the quest chain. The easiest way to do this is to keep her CC'ed, as she will heal the Emperor otherwise.

13,900 XP with 2.3. Another 13,900 to go talk to the king in ironforge!

Did this as a level 80 H priest for Loremaster. You would need Shadowforge Key, and health pots, fire shields, or something to keep you viable through lava:

1. Take the easy way to the boss: Enter instance, go left, unlock door. Take the tunnel to the Dark Iron Highway, and pass the mobs (or kill them, whatever) to the opened doors at the end of the Highway.
2. You'll see Lord Incendus. Kill him, or avoid him (whatever) and jump off the left side of the platform into the lava. Since I'm a priest, I used bubble and renew and I was just fine.
3. Swim North-East in the lava until you see a bidge to your right. Swim just under the bridge, there is a ramp out of the lava on the east side.
4. Enter the hallway, kill Magmus, enter torch room.
5. Kill the ""red guys"" in the torch room- they are the only mobs that are RED and move, so they're easy to ID. Kill 2, loot the torches, and set the blazier afire. The door behind you will open.
6. To be safe, kill the mobs in the room with Thaurissan- while an 80 plate wearer might be able to tank the boss, and the senators (and other adds) it's just easier to clear the room first.
7. Blow the boss up, and when he's dead, Moira goes green. Turn in quest, and presto!

Go go Loremaster!