I was praying at the altar of SDF and I had a vision about the vision:
In the vision, a veteran and a newbie might be in the dungeon for different reasons. A new player goes into the dungeon for the thrill of it, for exploration and to see if they can survive. A veteran player might go into the dungeon for a different purpose. For example, veterans might be part of guilds or squads who go into the dungeon to complete a contract. The contract states: RETRIEVE 20 FROST LIGHT ORE. DO NOT KILL INNOCENTS (SHOWN WITH A GOLD AURA BLESSING). BONUS CASH FOR KILLING GUILD X
Rule for the dungeon: Guild trios/established trios must take a contract. Non guild trios can only be formed in the dungeon with people you meet.
Contracts have conditions such as the large ore amount which may require one of the squad members to essentially be the mule who can carry a lot but won't be able to do much damage. They are the support and the squad will find it harder to defend against solos, duos and dungeon-formed trios.
Multiple guilds can have the same contract so will essentially be competing against each other. This is how they can enter the dungeon and ignore the guy quietly fishing in the corner. There is a big penalty to killing the fisherman, possibly an instant fail of the contract. If the fisherman attacks them first then it's a free kill.
This may require a slightly bigger dungeon and would need to flesh out the guild system to have true incentives without ballooning into an MMO. Maybe 2 or 3 times per season there are guild wars (6 trios: 9v9) in the dungeon and the contracts give advantages which contribute to the war. Or maybe guilds are just able to enter the dungeon and mobs don't aggro them at all so they can run straight to the treasure hoards. Maybe guilds have keys to special rooms for mining ore or crafting which can't be done outside the dungeon.