Going to keep up a list of zones, NPCs, questline and the like, in case people want to either get their Demon Hunter itch satiated or when Legion comes to take their DH through old world.
Just remember, even with this list, YOU ARE NOT PREPARED!
Quests:
Alliance Only: Ghosts in the Darkness More of an achievement than quest. It is done in Darkshore, in the Maw of the Void.
Horde/Alliance:
Deceivers in our midst
Demon Hunter NPC Feronas Sindweller given questline in Felwood. Start out by doing -
Squirrely Clean
Running the Course
Weeding the Lawn
You take on the guise of a Demon Hunter, and eventually fight as Illidan in his battle with Tichondrius.
Altrius the Sufferer is a Nelf Demon Hunter who once worked for Illidan but now fights agaisnt both Illidan and the Legion. Tons of quests with this guy. Found in Outland Nagrand 27.4 43.0 Also leads to the Varedis/Book of Fel Names questline.
The Hunter and the Prince relive the battle between Arthas and Illidan, this time as Arthas. Starts here.
Zones: Zones that have a general Demon, Illidari, or Legion theme to them.
Felwood
Blasted Lands, non Iron Horde version, fighting Demons all ober, including Loramus Thalipedes questline.
Most of TBC, specifically
Hellfire- the whole zone, but that is mostly Fel Orcs, but Socrethar is here too, and the Throne of KJ too.
Nagrand- see Altrius above.
Shadowmoon Valley- Demon Hunter central.
WoD areas- Taanan Jungle, Talador, Shadowmoon for Alliance
Dungeons and Raids-Nearly all Raids in TBC, some dungeons:
Raids
Karazhan - Terestian Illhoof, Prince Malchezaar
Sunwell, all bosses
Black Temple - duh, Illidan/Glaives!/Eyes Or Sageras, Council Fights, Reliquary
Mount Hyjal - bad raid, good lore
Serpentshrine Cavern - Leotheras the Blind, insane Blood Elf Demon Hunter
Hellfire Citadel
Dungeons
MgT- more general Belf theme, but leads to SWP
The Arcatraz- Demons everywhere
Well of Eternity- fight side by side with Illidan, dont forget your glaives.
AU Auchindoun
Lemme me know if I missed anything.
Updated.