Technically, this isn't true. You can clear all of the turns of Final Coil of Bahamut perfectly fine in full i110 gear. Evidence here:
https://www.youtube.com/watch?v=NoXz...TQj13CHjJxD04w
I see very little reason to up the cap of Poetics to 600. Raising the cap any further than it currently is, you might as well just remove it entirely and just let people grind to their hearts content. Gear alone doesn't make the player. You still will need a competent group to complete Coil regardless of gear. The fact that there are groups out there that can clear T1-T5 of Coil in i55 gear and T10-13 in i110 gear is evidence enough that it's not gear bound. Gear helps, but you still need to play your role and have others that do the same.