It seems intriguing, but I take issue with the values suggested. I think it should be fairly easy to calculate at level 40 how much more experience per level, and at 30, and at 20, an item level multiplier must be applied to the DC, GDC, IDC. The initial base multiplier will be harder though, because you need to know exp/180mins for FATEs and then exp/180min on dungeons. The calculation for banners should be easier to do than the above because equating exp chains to FATEs uses essentially similar pacing and mechanics.

Makes little sense to have xx% chance to drop seals, since the seals could be scaled relative to the full chance you get in FATEs.

I am intrigued by the gameplay aspect, but think it needs more careful balancing.