1. Get hit capped for content you run. Once you are 0,01% over hitcap, any additional point becomes totally useless.
2. Intellect is always much better than any other stat.
3. Haste is very close to mastery, and depending on your gear one will top the other. It's even encounter dependant. A general rule of thumb is that haste is always better than mastery, but that is not always true.
4. Crit should always be reforged away.

Gemming should be pure int, unless a socket bonus is worth it. (red/blue socket with 20+ int socket bonus should of course use an orange gem in blue cause net int result is the same).

Best way is to use chardev and then simcraft the profile to see your statsweight for your own gear.