This post is horribly late. I actually got Machinist to level 70 a few weeks before Shadowbringers released. As I mentioned earlier though I wasn't in the best of mental states so I didn't write anything back then. Then I sort of forgot about it, started playing Shadowbringers, finished it and got my Machinist to 80... Oops!
Since Shadowbringers switched to a role-based questline for levels 71 to 80 and Job Quests now consists of only one quest at level 80 I will include that one in my usual recap of the Job Quest story here too.
WARNING: Spoilers about the Machinist questline from level 60 to 70 and the level 80 quest ahead!