Pre-order Bonus: A higher difficulty mode.
This bonus simply unlocks the hard setting upon purchasing the 'deluxe edition'. Rather than making you play all the way through to unlock the setting—which as a hardcore gamer, you're probably going to do anyway. So for the serious gamer it shortens the lifespan of the game giving you no reason to replay.
Thanks, but if I wanted to slog through an unknown game while using the tears of failure to lubricate my controller I'd stick with Dark Souls.