If you are talking about randomization, I'd love to not see the mobs on the way
but randomly spawn next to party and randomly targetting party member until somebody get higher aggro.

Density of the mob spawn can be different in each area in dungeon (may be one mob spawn every ? sec)
and of course there should be maximum number of mobs on field at a time.

You need to fight your way through the dungeon until safe area i.e. before boss room (familiar to normal FF feeling now?).