Rarity

[Vidu]

You forget the real obstacle before starting the grind:
How to unlock Mentor-roulettes.

->One must have completed all dungeons / normal trials / 8-men-raids / 24 people-raids and all old Ex-trials (which is at the moment everything from ARR up to Stormblood) to have access to the roulette.

EDIT: Or, in short, you need to complete everything that isn't Savage-, Ultimate- or current Ex-content.

I kinda assumed that someone whos looking for things to keep them entertained that requirement wouldnt be to much of an obstacles, to be honest. Unlocking and clearing all of that content seemed like something one would do before looking for rare stuff to grind out - and even if OP doesnt have everything unlocked, they said they dont mind a grind. They did mention though that they usually restrict their characters to specific jobs/roles - something you cant do if you want mentor-status. So that might actually be the bigger problem here, before we even talk about the other conditions involved - like the 1.5 commendations and the 1k of completed duties or, in the end, the requirements to unlock the mentor-roulette.