Take a look at the second graph in this post mate:
https://forum.supercell.com/showthre...1#post12711564
It still is very preliminary, but I think there's reason to suggest that the defensive gaps are largest in the middle leagues. Because offensive strength can be assumed to largely follow the defensive strength (although much less reliably), we should assume the biggest offensive strength gaps to also be in the middle leagues.
Granted there probably is a gap somewhere up in Masters, but I'm wondering if it's not more appropriately labeled a 'skill' gap.