Curious about leveling speed

[Nominous]

This is what I'm talking about: everyone claims "it is possible" yet few if anyone has done it. Everything's based on leveling alt classes which has the powerful Armoury Bonus.

What are you trying to accomplish, prove, or learn here? Are you trying to prove it isn't easily done? Or are you trying to learn how to do it yourself? Most people saying that they hit 50 in 3 days are talking about after their first capped Job. That doesn't make it any more relevant, which is what I feel like you're getting at.

The majority of players have a capped Job already, and that's the most important asset to leveling to 50 in 3 days. Otherwise, the other bonuses kind of pale in comparison. Other than the 50 bonus, here's what you need to fast track to 50 in that amount of time.

1) Have 99 leves stocked. 1-21 can be done in roughly 3- 3 and a half hours by completing leves such as, "Adamantoise Tears", which can be done without combat, and only take around 50 seconds (at max).
2) Hit up FATES while queued for dungeons, at this point. As long as you get decent credit, you're not missing out on EXP. However, if you have an FC party that will boost you, simply spam dungeons until roughly 30-ish. That's probably a solid 8-10 hours out, depending on how fast you complete dungeons. At which point...
3) Either you grind Coerthas FATES, or you continue doing dungeons, however... dungeons will take slightly longer than organized FATE grinding. This is until 41 or 42, which should take you another roughly 15-20 hours.
4) At this point you can FATE grind until 45 (about 7-10 hours depending on your dedication), and then you can DD run spam, which takes no longer than maybe 5 hours to hit 50, with a WHM/good party.

That is how you hit 50 in 3 days. The times are a bit off, I know, but the general idea is there. I didn't hit 50 in 3 days when NIN came out, but I was at roughly 40 by the 3rd day, it really isn't that difficult. Anyone trying to hit cap from a brand new character will never hit it in 3 days, it's impossible. You need the dungeons, which are unlocked via story, and there's Primal fights mixed in with that, not to mention tons of running tea around.