Travel

[Jakensama]

I wouldn't have a world as Dense as say the Barrens. While you do want some wandering NPC's and you want some dungeons etc in certain lands you don't want it packed to the rim like most WoW zones either. You want some space for new factions, places for Guilds to build villages or increase the sizes of those that currently exist. I would certainly fill it with things to make it interesting to hold onto a zone but as you said the front is always moving.

I think mobs should expand to fill the space available to them, in new or undeveloped areas there are going to be more mobs, if you want to build your village there or expand it, you should have to secure some land and chase off the mobs. If enemys raze your village and don't leave anything left there, the wilderness could expand back over it.

Not sure how dynamic and roaming mobs would work out though, you would have the problem of things going extinct and eventually players just hunt the world dry so you definately have to limit the developable land (or else end up like original UO where every square foot of clear land in the world had a house built on it).

If you make it too sparse the game is boring, running around long distances with doing nothing is boring and certainly not a rewarding way to play a game for many people - you have to suspend some realism for the sake of enjoyment.