Weapon damage won't matter much. For example, if you have about 100k Vengeance from the boss and 30k Attack Power on you gear, replacing a 463 polearm by a 517 weapon (like Gao Rei heroic, upgraded 2/2) will increase your dps by about 8%.
Haste doesn't increase Brewmaster dps a lot. And you certainly won't double your crit with t15 gear.