We're talking a double header of discount here. If you just feel like trying the game out, then a Steam Free Weekend would probably hit the nail on the head for you. Want to pick up the game in all it's glory? It's 50% off (DLC too) now through 1pm Sunday (PST) on Valve's network.
To celebrate, Dungeon Defenders is this week’s Steam Free Weekend game! Download and play for free from today, Thursday the 15th of March, through 1pm PST Sunday, the 18th. During that weekend, players can choose to purchase the game and its DLC* for 50% off!