I've been trying to get people to dal for a while now, it's just too "inconvenient" for people to have to go through a couple portals from a level 90+ mage. Realistically dalaran is an ideal place to be, especially for people on PvP servers, because there's no ganking from high levels with it being a neutral zone, a guild bank / regular bank / mailbox IN THE SEWERS and an AH up on top in each factions respective area, plus it's cross realm so you don't need to group up to see eachother in the city and duel nubs from other servers. I started coming to Dal on my horde just to AFK months ago because I knew there wouldn't be 100s to gank me when I got out of a BG and had PvP on unintentionally... Not to mention having hearth set to shrine is just more convenient in every possible way, Orgrimmar is wasteful to set hearth to at any level.