Mordecai ability acts only on magic. So it would depend on the source of the werewolf/shifter's ability. If they are a born shifter, (that is, they are a shifter by species), then a mordecai would have no effect on them because their ability to shift isn't magic...it is a trait of their race. Same thing with vampires.
But on the other hand, if a person were under a curse or enchantment that caused them to shapeshift, then the current transformation would be negated by a mordecai's presence. If an undead creature were animated by enchantment, that too would be negated, and they would likely simply become a corpse once again.