ArenaNet has posted information on the Guild Wars 2 website explaining how crafting mastery, and crafting a legendary weapon, will work in the Heart of Thorns expansion.
There’s also information on the new Map Bonuses system, which will make acquiring crafting materials a more “directed activity” and streamlined experience.
The new system will also add regularly rotated bonuses to explorable maps, and will reward players with crafting materials for completing events.
It will also offer players an incentive to return to areas.
With the expansion, Guild Wars 2 players will also be able to invest Mastery Points into the legendary crafting track.
There’s plenty of information available on the above through the link.
Screenshots for Precursor crafting are below.