Quick and Dirty on the [H] Halls Bosses of ICC

[Dianora]

On the Wraith of the Lich King encounter, the alternative method of dealing with the wave of mob is this:

Instead of following Jaina/Sylvanas, stand by the clearing near the edge of the cliff in the back (ask your party NOT to fall through the cracks). Wait for Lich King to start summoning and then go out to meet them. This has the advantage of actually speed up the encounters, as you can now run behind the Lich King if you have sufficient amount of DPS, and you can run up towards him, as the mobs will spawn near him.

If you have sufficient DPS, you should be able to clear the whole place and get the achievement.