Legendary prec. crafting mastery.
I detest grinds, and I detest luck.
No sentence has summed up these forums with more truthiness than this one (hey, truthiness doesnt come up as misspelled in chrome, neat). But hate it or not, no way around it.
Also, to your question about choosing what your xp goes to, yes you will be able to.
80 Mesmer – Yaks Bend
It seems like it (the mastery) will not be really grindy. Considering that there are so many prerequisites, including several items to be collected, you will require to do a number of different activities. Though, how you acquired these items can possibly be grindy, but I have no say about that yet.
But of course this only apply if your definition of grinding is repeating the exact same activities in order to get to your goal.