I’m not very good to give an opinion about this.
I play one only build with the Marksman. Apart from that, I don’t like this mastery (and even the class, in fact). It’s the best designed class in the game, but I don’t like the “shoot and flee” gamestyle.
The only Marksman exception I found is this build, based on Reign of Winter:
The core skill is Detonating Arrow, which is a very nice skill.