Nexus owners

[DoubleT]

Atma - 2 - 5 days (depending on your luck, I can see this going on for a whole week)
Animus - 7 - 14 days (depending on how much you burn, I can see the extremely hardcore getting myth + book clear a day + accumulation of some more Myth before calling it)
Novus - 9 - 12 days (assuming infinite Gil to buy all the materia needed and doing the daily + myth farm, I can easily see 6-8 Alex a day @ around two hours Alex)
Nexus - 4 Days (as shown)

your math is flawed. during the 14 hour atma challenge the guy got 11 atmas in 14 hours so it is entirely possible to get all 12 within 24 hrs. A friend in my fc got 3 animus's completed in less than 2 weeks. and if i remember correctly the first novus's showed up within a week of their introduction. So if you were to go hard enough, you could finish in way under the time that you mentioned. As for coil, i dont remember exactly how soon after release that BG beat t9 for the first time, but i do remember that it was significantly faster than the time it took them to get the first t5 win. Either way, comparing coil gear to tomestone/relic gear is pointless in my opinion. They both involve grinding. Either grinding the quests/dungeons for one, or grinding deaths against a boss for the other, its all the same.