You might not have played SOULFU - Secret Of Ultimate Legendary Fantasy Unleashed (PC)

SOULFU is a game developed by Aaron Bishop who is currently working on the Sandbox Game Lords of Uberdark, which might also be worth looking at.

Gameplay: Dungeon Crawler, Coop, Third Person
The objective of the game is to explore a dungeon and get as far down as possible before you die. Along your way you have to defeat several monsters, bosses and avoid traps. To survive this endavour you can play together with 3 of your friends in a hot seat coop mode using keyboard and joypads. There is a good variety of classes to choose from that all have interesting unique features. The dwarven character for example, is able to resist poison, while the hobbit character is able to see traps.
Since the game is very punishing on character deaths (experience loss) and quite challenging in the lower levels, you will start the game over to perform better on the earlier levels and conserve more ressources. The game manages to stay interesting though since you can mix up your class composition and you can hope for more nice loot in the next run.

Download: Windows/Linux/Mac - Windows version with the option to save the game.