The Delicate Sound of Thunder

Here's a simple way to reach the cave, as discovered by a friend:

Get to the scaffolding with the three blast-off runes (you can get here quickly via the single rune at the ground floor of the excavation site).

Choose the middle rune. When you land, head several paces to your left. The cave entrance should be on your right.

71.6, 69.8 inside the cave at the Baelguns Excavation Camp.

After passing by on an army of Dark Iron Dwarves an holograph titan appears talking to the crowd. After listening to the following lines, you get the quest completed.

Kronus yells: [Titan] Come, minions! Your master calls!
Kronus yells: [Titan] The work of your brothers in the Storm Peaks has reached a frenzied pace. Soon, Father will be freed.
Iron Rune Worker says: [Titan] Stop! Stop! Scrap metal moves itself now?
Iron Rune Construct says: [Titan] To interfere with construct's function results in termination. Move along.
Iron Rune Worker says: [Titan] Forgive my insolence!
Kronus yells: [Titan] Your brothers to the north have subjugated the stone behemoths and set them on the path to Ulduar. Soon, the remaining defenses of the Pantheon will be neutralized.
Kronus yells: [Titan] The three fissures opened by the mortals of this region must be silenced. The earth hears and sees what we do and will continue to interfere with our efforts if the way is not closed.
Kronus yells: [Titan] Bury this place! Your master demands it!

Complete directions:

- top of entrance to Excavation: 72.7, 67.5.
- take scaffolding all the way over to elevator at 72.3, 74.1
- take elevator down.
- get off elevator and jump down to scaffolding at 72.5, 73.9
- face relatively north and take ramp to right.
- you will take two ramps... after that go to the right.
- jump to scaffolding at 72.8, 72.2
- face the cliff wall and take the scaffolding / ramp up to the right. (There will an earth elemental stationary at the base of that ramp.) Base at 72.9, 71.6
- go up the scaffolding to the green dirt at 73.8, 71.0
- take scaffolding ramp on your left up to the deck.... you will come up to that deck underneath the next ramp you need to take.
- the ramp (base at 72.9, 71.2) up to the cave entrance.

Hope this helps... a little complicated, but hey... better than nothing.