The soldiers and knights are also near-100% rips from FFXIII, my theory being that these models were chosen because they were finished (either from being in FFXIII or being meant to be used in the lightning fate) and could be implemented easily. Due to the time constraints of going from 1.0 to 2.0 fast, they had to create the end-game as fast as possible and since it would be the content that people would A) See last, and B) See the least, they propably had to use existing models rather than create completely new creatures.

Aside from the ADSs and Turn 5's boss, every creature in the coil is a reused model.