April 2016 Card Nerf
It was announced on April 20th, 2016 that Hunter's Mark would receive a nerf.
- Mana cost increased to 1, up from 0.
Quote from BlizzardHunter’s Mark is an important option for Hunters, but it’s too efficient at 0 mana. We are increasing its cost to 1.
The level requirement should be listed in the "quick info". I was very confused as to why I couldn't craft certain cards.