Why is mastery so good?

[Zalifur 0]

Hi, I just have a question about mastery as Outlaw. 

Why is it so good for me? 

http://us.battle.net/wow/en/character/scarlet-crusade/Zalifur/simple is my armory. I have an 830 versatility trinket that Mr. Robot says is better, so I'll probably swap one trinket for that and an 835 Rough-Hammered Silver Ring that would be approximately a 100 dps increase replacing my Grubby Silver Ring. Why is this? Any help would be greatly appreciated, I don't really simcraft, I used shadowcraft in the past but it seems a bit unreliable at the moment. 

[Carrn 284]

2 hours ago, Zalifur said:

Hi, I just have a question about mastery as Outlaw. 

Why is it so good for me? 

http://us.battle.net/wow/en/character/scarlet-crusade/Zalifur/simple is my armory. I have an 830 versatility trinket that Mr. Robot says is better, so I'll probably swap one trinket for that and an 835 Rough-Hammered Silver Ring that would be approximately a 100 dps increase replacing my Grubby Silver Ring. Why is this? Any help would be greatly appreciated, I don't really simcraft, I used shadowcraft in the past but it seems a bit unreliable at the moment. 

A 100 dps increase is effectively nothing.

Mastery is a free hit with your offhand any time you attack or cast an ability, and adds up to a decent amount of damage

[Zalifur 0]

Thanks for the reply, Carrn! 

I know what Outlaw's mastery does, but on Shadowcraft, Mastery is my highest weighted stat other than Agility, with Versatility as a close second, then Haste, then Crit far behind, and it's even telling me to gem Mastery. Is this correct? How all-out on the Mastery train should I go, if I do?