Any quest that is triggered in an area where it doesn't actually happen should have a second trigger as well.
For instance if you want to raid the duergar fort, you shouldn't have to walk into Upper Sanctuary (which is probably off limits to half the server population nowadays) and speak to the shield dwarf.
Another shield dwarf could be found somewhere in the wilderness, or a Duergar in Mur could hire you to wipe out a rival clan, or just a simple exploration trigger.
It is getting really difficult to quest nowadays with quest givers dying, joining rebellions, or being locked in inaccessible areas. This would go a long way toward addressing that.
Consider that for those who can't enter Upper because the Spellguard doesn't approve of their hairstyle, and aren't strong enough to survive lower (anything under level 20, really) that for them the majority of quests in the module have become off-limits.