I haven't played DFO, but I think it looks a bit like this.
I've seen it described as the following by Maurice_T from another board.
"Sacred Citadel is a 2D side-scrolling co-op brawler/beat ‘em up for up to three players. It’s being developed for PC, Xbox Live Arcade, and PlayStation Network by Swedish studio Southend Interactive, who have also worked on XBLA titles like R-Type Dimensions and ilomilo. Besides having arcade brawling action, Sacred Citadel will also contain RPG elements like XP, stat points, leveling, and new weapons to find. "
Here is an article about it
Oh and the best news is about Sacred 3 being slated for 2013.