Read the build on twinkdb. Batresh explains it well. I have the same build on my dh and it does nice dmg. But unless you really like DH I wouldn't recommend the class. Feels lackluster without high level talents.
The twinkdb build says get 25% haste then prefer mastery. Is this because of diminishing returns? There's a reddit post talking about it from 2 years ago but i don't know if this is still the case.