I used to have a tough time figuring out how to do the Hand of Iruxos quest, or the equivalent for the Alliance (its name eludes me right now). It is completed in the center of the first building at the entrance to the Thunder Axe Fortress in Desolace (around 55, 24).
Approaching the Fortress is no big deal; I used my Mana-efficient Aspect of the Viper method, which involves shooting to pull, backing up while the cat gets aggro, and then finishing off. As long as there is clear space behind you this method works well.
Once you get past the gates it is important to clear the whole area by the door to the building, because you need to be able to back up if the mobs inside the building come after you. After the outside area is clear, you need to watch for the single mob that circles the hallway. The building is round, and the hallway circles the central room. There are also stationary mobs in the hallway, but these need to wait until the patrolling mob is taken out.
After you get inside, you need to work fast, as these mobs respawn very quickly. I like to switch to quick-kill method, which involves sending the cat and setting Hunter's Mark at the same time while using Aspect of Hawk. For the first mob should be shot a little before the pet gets to him, as you want to pull the mob away from the other one behind him, to avoid doubling up. Once he is done, turn around and take care of the one behind you. Now you have room behind you regardless of which direction you decide to take. Working quickly, go around the hallway and clear out the mobs.
Getting into the room can be a bit tricky, and don't be surprised if you pull more than one mob. Set a freeze trap, and send the pet in and hope for the best. Be ready to feign, but do so out in the hallway. As long as none of the mobs have respawned you will be fine.
After the mobs in the center room are clear (Horde can ignore the Alliance NPC; it is there for an Alliance escort quest that you can be happy you are not doing), click on the red crystal in the center of the room, and be prepared for a tough fight. I prefer to stay back and work with Viper Aspect again, which lets me use lots of Mana for Arcane, Serpent Sting, pet mending, Concussive and Multi-Shot. Again, Feign Death can be useful here, but it may be resisted because of the level difference.
When you have finished the demon, loot it for the box, and get ready to fight your way out. Even if you did this at top speed they will be respawning already.
I did this as a Level 33, and Feigned twice due to my own mistakes, but did not die at all. At the same time I took care of the "Burning of the Spirits" quest (while I was outside, as it takes a little longer to kill the mobs while collecting the gems), and the "Sceptre of Light" quest at the top of the tower to the left of the gate once you get in.
Just try to pull one at a time, go through the mobs quickly, and all will be well.