Well, not all classes can use all their skills in battle. I guess that's the case with the SH too.
For example, Fury Warriors have 5 masteries and 2 stances. They can use only 1 stance in a fight and obviously, since they choose to use a certain weapon, they "lose" the other 4 masteries. Ghost Stalker also has 5 masteries. Guardian has 2 stances and 4 masteries.
Generally try to measure each class's pros and cons as a general, not just by the number of skills they got.