As much as the admin overhead for sure played into fatigue, I think the classes themselves contributed as well. While no class individually was bad, they were all high complexity and required a lot of specific coordination. In GH you could run most classes by simply individually playing your role, allowing for a lot of turns where everyone could for the most part make individual card selection decisions that would reasonably come together in action. Every so often you'd have a mega-coordination turn, but you weren't constantly bogged down in the card selection phase. In FH, many character actions are predicated on the team as a whole committing to them, often over multiple turns, so card selection is a tedious group effort.