Now admittedly, this isn't the best way to determine who will be important or vital in the course of Evercold. This is using the Duty Support as some basis but nothing is concrete.
  • Alphinaud 34 duties 31 dungeons, 3 trials
  • Alisaie 32 duties 28 dungeons, 4 trials
  • Y'shtola 25 duties 22 dungeons, 3 trials
  • G'raha Tia 20 duties, 17 dungeons, 3 trials
  • Thancred 18 duties 16 dungeons, 2 trials
  • Urianger 16 duties 14 dungeons, 2 trials
  • Estinien 13 duties 11 dungeons, 2 trials
  • Krile 13 duties 10 dungeons, 3 trials

This has been the distribution with all the expansion with retroactive addition of the first three expansions throughout the years of the scions. Again however, can't really use to say who's going to be important considering Thancred and Urianger were on the key artwork, considered Key characters, and in the end, had the least amount of impact on the whole story of DT.