How is Mastery Rank calculated.

[Avereith]

We've also had people rank up just from activating homepoints for the first time, so it's more than just titles. It really is just a background point system that we will never ever ever figure out if the points are at all weighted towards certain content.

"I just unlocked homepoint to Attowah chasm and received a rank up from 4-5"

Also it's not pure titles because we have another player working this out with is that has just as many titles as the rank 8 guy and is still rank 7

[Alhanelem]

We've also had people rank up just from activating homepoints for the first time, so it's more than just titles. It really is just a background point system that we will never ever ever figure out if the points are at all weighted towards certain content.

"I just unlocked homepoint to Attowah chasm and received a rank up from 4-5"

Also it's not pure titles because we have another player working this out with is that has just as many titles as the rank 8 guy and is still rank 7

You didn't read the dev post did you?

They listed off tons of things that contribute to mastery rank, including unlocking home points etc. And they noted that titles are heavily tied to content completion and thus are something you want to go after.

You wrote this post as if you just discovered these things, but they were covered in the official post. blold/underline emphasis mine.

Greetings,
The following is the extent of the information we can share regarding Mastery Rank.

• Accumulated playtime
• Mission progress
• Number of completed quests
• Combat and magic skills
• Synthesis and fishing skills
• Number of Trusts obtained
• Battle content (Such as Dynamis, Nyzul Isle, Moblin Maze Mongers, Otherworldly Skirmishes, Omen, etc.)
• Non-battle content (Such as Chocobo Racing, Mog Garden, unlocking Warps, etc.)
• Titles almost always correlate with content completion; titles obtained upon completing content are tied to Mastery Rank.
  
  One example is the Expeditionary Trooper title that is obtained upon completing Expeditionary Force.