Mmmm idk I think 8 is fine per season.
Getting a fort score and tyran score for each of the 8 dungeons is enough imo. That’s 16 scores total. Increasing it to 24 seems like a lot.
Now having 10-12 dungeons per expansion is another story. We’re on track to do 8 + 2 from mega dungeon. I could see them adding another 1-2 towards the end of an xpac would be cool to bring us to 12 total for an xpac.