The basic concept of Mage Wars RPG is going to be citites and wilderness areas. The wilderness should be large, intricate, and full of fun options for exploration.
Nearly all the instanced dungeons will be located in or very close to major cities. That is to say, all of the instanced quest-content. Anything the character would be expected to visit more than once should be within a reasonably short walk from a portal, and they should NEVER have to fight their way through a bunch of enemies just to reach a dungeon entrance.
The bulk of the wilderness will be non-instanced and finisht his later.
Ideally, players should be able to travel over the whole world, particularly in skyships. But, if their ships crash, players fall off, etc., they should not either die or find themselves in a completely empty region. Rather, the vast swaths of land should be populated by hostile enemies.
Mage Wars RPG will include basically the entire Greater Continent, but only the main areas like the Agras Plain and Sun's Beacon will be immediately accessible. Large, unimportant wilderness areas will be programmed procedurally, meaning mobs and some things like minor villages and dungeons will be generated automatically.
Mob spawns will be controlled by population, meaning the more players in an area, the more mobs will spawn.
Keep in mind that everything south of the Barrier Range belongs to the Marcons. If we could find a way to spawn entire working systems, towns and villages and farms, all with destroyable buildings and infrastructure, we could have the most fantastic end-game content ever created. Each guild races against other guilds to see who can wreck the most Marconian stuff; explore the most regions outside Marcon territory; and collect the most treasure.
The large areas need to be produced using a combination or procedural and hands-on design. Procedural-generation can fill in the bulk of the worl while a team of coders and designers works to add high levels of detail. These teams should be given high levels of autonomy in order to encourage creativity. We have a very large world to fill in and only a few major cities to consider.