Werewolf is the first of two shapeshifitng skills the druid possesses (the other being Werebear). It transforms the druid, giving him increased proficiency in melee combat. Melee druids often focus on one of these shapeshifting skills.
Although Werewolf gives an increase to Attack Speed, Werewolves and Werebears swing more slowly than the Druid in his natural form. This gives the impression that the Attack Speed increase is not working, since the player will notice the Werewolf is hitting slower than the Druid at level 1. However as more points are poured into this skill, the attack speed will quickly reach the druid's and pass it.