Yeah, you'll need a player to be the overlord for Descent. The more I play it, I think second edition may be better than first. The second edition is ranked higher on BGG by a fair margin. It's hard to say really because they each have their pros and cons. We also end up "house ruling" both editions to one degree or another. That's really the thing to pretty much every modular miniature based board game I have ever played though. You and your group have to not be the type to rule hunt and bring the game to a screeching halt when the rules aren't crystal clear in certain scenarios. You have to be able to throw out parts you don't care for and even create a new rule here and there. By doing those few things, any of these types games can be amazing. When I play with my family & friends, it's about creating those perfect moments within the game that people will reflect back on with a smile. The environment has to be right to create those types of situations, and rule nazis need not apply. The type of scenario where the hero is able to be exceptionally heroic, or when the overlord's well laid plans finally come to fruition are what these heavily thematic board games are all about for me and my group.
If you're looking for games to play co-op in the same vein as a dungeon crawler, I would suggest Gears of War. I believe the D&D board games Legends of Drizzt, Wrath of Ashardalon, and Castle Ravenloft all have co-op. Someone back me up on those, I have yet to buy or play them but I think I read that when looking at them in the past.
As an FYI, Mansions of Madness also requires an "overlord" player.
Good luck and have fun.