Ask a Thief Thread.

Yes but more levels = more luk = more maximum damage. Your damage increases but you don't have any skills that raises your mastery beyond 60% like dark knights or bowmasters. Ask any level 15x hero and they'll say they don't like their mastery and damage range.

Dark Knights are stable. 80% mastery, max and min damage have the same multiplier (5.0*str) Bowmasters aren't because our criticals do 340% while our normal arrows do 100%. Even with 90% mastery our lowest hits are incredibly low. Shadowers are kind of in the middle.