Hum... talking about Dungeons: I'm currently in the Academy and it's really getting a bit much to be real fun.
So "Story Dungeons" should get a special treatment as well. Maybe define a pool of enemies that CAN spawn and if those are out... like three full spawns and then you did enough grinding. Or tie the respawn to story events (riddles solved) and do not load "random enemies" but a bunch of story-groups. As the academy is right now it feels like "stretching game time" with waves upon waves of enemies.
Given how many nice quests are to be found in the city, this is not really necessary to make it worth my money.
