Because WoW existed before the Manga, Quel’Danil existed before Burning Crusade, and because the Devs couldn’t be bothered to update the lodge’s appearance in Cataclysm.
Farstrider is still there. Quel’Lithien is now largely filled with Wretched.
The lodges existed as locations for the High Elf Rangers during the Second War. They’re outposts that were meant to keep an eye on the movements of the Orcs.
Fading?
It’s just not relevant. Nothing more than that. The High Elves aren’t a united people. The most active force of High Elves are the Silver Covenant, but not every High Elf exists under that flag. The Highvale elves don’t have a reason to join with, or ally with the Silver Covenant.
Blizzard should update the heck out of the Hinterlands to be like mix of everything. HD Stuff of the Amani, Ruined Night Elf Buildings from Broken Isles, Tall Pine Trees, Blood/High Elven Buildings of Thalassian stuff, and etc.
Sort of. Hordeside, you get a mission to retrieve some documents and instructions to kill a certain number of defenders, phrased as “kill everyone you see.” But the documents are the main objective, and (as Solarion notes), Alliance side quests imply that the lodge isn’t in fact wiped out.
ETA: Also, apparently Alliance side quests are about fighting off a whole army of Horde attackers, while the Horde quest is a solo mission?