A dungeon whose entrance only opens at a certain time (fixed or random) and closes after sometime but whoever got in can stay for longer time. Inside is a dungeon with random spawn point like TA but for party members and it's open PVP. It functions as a normal dungeon with mini bosses, trash mobs and one big boss but you can encounter other parties too and fight them. Make the paths and mobs random so no speed runs and parties have to explore and have more chance to run into each other. Also it should give rewarding loots.
I know this isn't feasible with the current population of the game, but this should help for longevity after guilds and steam. Oh and make it high level only so no whining.
Edited by Xian, 25 August 2014 - 16:21.