You are right length of time doesn't equate difficulty, I still don't think it should take an entire day or less than 24 hours to get a set. Certainly not three days either to farm one coffee either.
You are neglecting a critical point: the time sink of leveling. In XI you worked on obtaining your first set of AF as you leveled up through towards a level cap that was higher than the level range where you'd use AF. Leveling through the 50's combined with farming coffer keys stretched the experience out for quite some time. I know for myself, once I had a few 75 jobs, I could do a full round of AF in a day if I felt so inclined. Especially if I had one or two of the coffer keys in my inv already.
What you're seeing now is no different. The people who are blasting through AF are doing so because they are at the level cap. They can easily put together a pt that can take down the bosses. They also already have gear with enough materia that they probably won't wear the AF. This is no different than in XI when you cleared your AF quests and used maybe 1 or 2 pieces and stored the rest because it wasn't useful at the level cap. They are interested more in the cool storylines and the new instanced raids that are supposedly much harder and will have gear that is more competitive with the melded stuff that everyone at endgame currently wears.
But if a person who leveling a class through does their AF for the associated job while they level through (like you did with your first job in XI) it will get stretched out by the leveling process. Now granted it won't be nearly as long because leveling in this game is much faster than in XI, but the experience itself is quite comparable.
My experience: I have 2 lvl 50 jobs (one being THM). I did BLM AF in about 8 hrs. Part of this time period was needing to clear DZ Darkhold which, in itself, was a fun dungeon crawl, but many people at the cap have already done that quest. To be honest the AF quest seemed time appropriate to me. I had a lot of fun, played in several completely different pick up parties of total strangers, and got my *** handed to me on the last boss for ~2 hrs till we finally got our strat worked out. It's meant as a waypoint because the cap won't always be level 50.
What I am curious about is what they will do about AF once this content gets nuked for 2.0. If the current content is supposed to be unplayable after 2.0, what then for AF? Not that I care personally, because I am enjoying it now and will have played through it by then. I'm just curious. It'll be funny as **** to hear all the whiners who return at 2.0 ***** about missing the content people are playing now when the could have just stopped QQing, paid 6.99 a month to play a fun game, and had their shot at it. It's got to be frustrating for Yoshi P- he's actually doing a really good job fixing Tanaka's near detonation of the game, but no matter what he does, he still gets grilled. He's managing to deliver good content on a game where they are changing the **** graphics engine and actual servers and yet he'll still undoubtedly get fried by the people who wait for 2.0 and then ***** about missing content. Poor guy can't win haha.