The problem is how fatigue and the ratio intersect.
Week 1: to get 100 Dragon Points, Earth exalts 100 dragons and Light exalts 300 dragons.
Week 2: to get 100 Dragon Points, Earth exalts 111 dragons and Light exalts 300 dragons.
Week 3: to get 100 Dragon Points, Earth exalts 125 dragons and Light exalts 300 dragons.
(That's assuming that I'm calculating fatigue correctly; maybe Earth only needs 110/120/130, or maybe it's 90% fatigue then 81% then 73% rather than 90%/80%/70%, but for the purposes of demonstration it doesn't matter that much.)
If fatigue went up much more dramatically, sure, Earth's size difference would get cancelled out more quickly, but the larger flights would be impaired by it much more dramatically also. Compare Shadow and Light:
To get 100 Dragon Points, Shadow exalts 165 dragons and Light exalts 100 dragons.
To get 100 Dragon Points, Shadow exalts 183 dragons and Light exalts 100 dragons.
To get 100 Dragon Points, Shadow exalts 206 dragons and Light exalts 100 dragons.
Flight culture and the difficulty of wrangling a lot of people and finding a time that works for a ton of people (rather than just a few) mean it's already pretty hard for Shadow to get double dom anyway. Imagine increasing it, or comparing Shadow to Fire or Water rather than Light!
Week 1: to get 100 Dragon Points, Earth exalts 100 dragons and Light exalts 300 dragons.
Week 2: to get 100 Dragon Points, Earth exalts 111 dragons and Light exalts 300 dragons.
Week 3: to get 100 Dragon Points, Earth exalts 125 dragons and Light exalts 300 dragons.
(That's assuming that I'm calculating fatigue correctly; maybe Earth only needs 110/120/130, or maybe it's 90% fatigue then 81% then 73% rather than 90%/80%/70%, but for the purposes of demonstration it doesn't matter that much.)
If fatigue went up much more dramatically, sure, Earth's size difference would get cancelled out more quickly, but the larger flights would be impaired by it much more dramatically also. Compare Shadow and Light:
To get 100 Dragon Points, Shadow exalts 165 dragons and Light exalts 100 dragons.
To get 100 Dragon Points, Shadow exalts 183 dragons and Light exalts 100 dragons.
To get 100 Dragon Points, Shadow exalts 206 dragons and Light exalts 100 dragons.
Flight culture and the difficulty of wrangling a lot of people and finding a time that works for a ton of people (rather than just a few) mean it's already pretty hard for Shadow to get double dom anyway. Imagine increasing it, or comparing Shadow to Fire or Water rather than Light!