An Update on Mac Support for Guild Wars 2
at level 80 I started training the Path of Fire Masteries, but locked my Heart of Throns story, should I complete the Path of Fire? (I bought both)
You can switch between them if you want to.
But with Locked you mean you cannot play HoT?
The only reason to play in order is continuity of the storyline.
HoT Masteries: You can start all masteries after you got into Verdant Brink using the opening story.
PoF Masteries: There are 2 things locked behind finishing that storyline. The Griffon Mount. You will not be able to go after that mount untill you finished Path of Fire entirely. The same goes for the Skimmer Diving Mastery.