I actually completed this quest line at level 50. This one was the hardest, but with a Totem of Wolf and "Help" on a hotkey to maintain the speed, I was able to run through the second cave to the door at the other end and get credit right before I died.

Warning: the creatures guarding the Silent City back door are level 53-55. On the bright side, they do not see invis, but some of the lower level Sul'Dal closer to the water do. --Unknown (Moved from quest page by --Virii 15:10, 9 December 2007 (UTC))