Shadow of Revan seemed to be about how well Theron, Lana, and the Player worked together when they weren't constrained by the traditional methods and leadership structures of their factions-- and their reward for succeeding was to be split up and placed in really high leadership positions within the structures that were holding them back.
Ziost showed Theron/Lana struggling to work within those constraints. Lana spends Ziost so overworked that she can't figure out that her second-in-command is a republic spy, and Theron gets everyone under his command possessed by Vitiate and killed.
I think post-Ziost, and especially into KotFE/KotET/Iokath, Theron, Lana and the Outlander realise they can do more for the galaxy outside of the Republic/Empire than within them.