In a recent 4Gamer interview, Dark Souls II Co-Director Yui Tanimura spoke about the title’s development and contrasts with the first game. In particular, Tanimura mentioned how they wanted to make the game “harsher;” described as imbuing players with “a sense of responsibility” in exploration and character building, as opposed to simply killing the player more. The elemental switching on weapons was mentioned as one example of such changes, encouraging the player to adjust their strategies over time.
Tanimura also mentioned efforts to avoid one single ‘best route’ to the end of the game; that no route is particularly safe relative to the others, and different players will find different paths easier to manage. Additionally, the change to invasion mechanics – allowing invasions to occur while the player is Undead – was made to emphasize the difference in statistics between Human and Undead forms; the idea being you may be attacked at any time, and so you may want to be at your best when it happens.