User blog:Heimdalsgate/Why is Dean vulnerable?

In Season 11 Episode 11 "Into the Mystic" Dean is called "vulnerable."

We know this because the Banshee tends to attack the weak and vulnerable. We also  see Dean become tired while helping Sam shovel.

This could be a result of his experience near the site of the "smiting" that was aimed at trying to destroy The Darkness or it could possibly be because of his connection to The Darkness, and the fact that he is weak because she is weak.

Does anyone else have any ideas?