With the current dev discussion and a, seemingly, very instanced-directed question in it, I tried to think up of a way to combine the freedom of L2's dungeons with the gameplay of instanced ones. The problem is, I'm not really a pver so I'll rely on
@Noaani and
@Azherae to tell me if this idea is complete shit and would never work as a good source of pve(x) content.
My paint skills are shit, but here's a top-down view of a floor of a tower dungeon (the same could work with layers of an underground one).

Here's a rough gameplay loop:
- each room has at least one spawn point of a group of mobs
- different rooms have different gatherables, trap mechanics, quest links
- room difficulty varies between 8-man to 40-man groups
- each room puts a marker on the group farming it
- if marked group stays within one room, the next spawn of the same mobs will have harder mechanics
- if the same group beats the room 3 times (could be more), a mini-boss gets spawned
- outside of the normal loot table, mini-boss drops a tool that lets you go through the hidden paths within that boss' lvl bracket (room type)
- if the mini-boss dies, the cycle gets reset
- hidden paths can be opened with a combo of utility abilities of classes (ideally one of each archetype, but debatable)
- if anyone in the room becomes flagged, a fast scout mob runs out of the room and yells in chat "there's a bloodbath near ___ mobs!" (or room name/location)
- mobs/boss aggro on flagged people first, but keep their anti-zerg mechanics at low strength
- if an 8-man room has more than 8 people in it for more than ~30s w/ 0 flagged people, mobs/boss start increasing the power of anti-zerg mechanics (same applies to 16/24-man rooms)
- the entrance to the next floor is in the Epic boss room
- anyone who beats Special or Epic bosses gets an indefinite pass to the next floor through the green hidden path
- green path can't be unlocked with utility abilities (also debatable, but I'd prefer if it didn't)
- Special bosses would respawn daily (+- a few hours from a preset time), Epic boss would respawn weekly
- final floor would have a Legendary boss with a several week respawn and a full room lock-out mechanic, so that its design could be closer to an instanced boss one
With this I tried to combine the endlessness of mob farm of L2 with a more pve content-driven design of "you do this sequence of events and you're done". A group could decide to farm the same room over and over until they drop what they need from its mobs/boss or they can try going to more difficult rooms if they're only interested in the pve fights themselves.
This would allow people to play from just 30min of "fully clear a room or two" up to several hours of "grind several rooms, while you wait for a special boss to respawn".
The flag protection is there to give the defenders some leeway if they get attacked by other players. It'll work even better if there's agro redirecting abilities in the game, so that the defenders could flag up on the newcomers (with no change in mob agro) and if they flag back - the defenders can redirect mobs/boss onto the attackers (with a boost from the anti-flag mechanic). But that move would still be dangerous because the scout mob would notify the nearest rooms about a pvp fight, so any pvpers around might come running in pretty soon.
So what do yall think, would this work as a dungeon design or does it lean way too much to the L2/pvp side of things? Oh, also, the mob lvl ranges can obviously be shifted or increased, same with room positions/amount - this was just a rough example.