The delay of two weeks was a necessary step, according to the company: "As we head into final preparations for launching the game, we have decided to move the launch date in order to allow us extra time to ensure we're delivering the most epic gameplay experience possible to our players."
Community Manager Piestro elaborated on the delay later in the announcement thread. "The transition from beta to live requires integrating with a good number of other systems. We are also planning to launch on Steam which complicates matters and requires other sorts of implementation work. Specifics aren't necessarily meaningful to those who aren't familiar with our internal systems, or particularly valuable. That being said, we aren't wasting this time and are definitely looking to see what else we can accomplish. More news later this week I'm suspecting."