That is one possible explanation.
A more plausible, alternative explanation in my opinion is that the new builds are far more powerful than the old builds and as such they represent a high percentage of the top 1000 leaderboard. Are there any facts to support this hypothesis or quantifiable data metrics to support this idea.
A simple metric could be top GR clear. Three classes had build(s) that were buffed in patch 2.6.7: Barbarians, crusaders, and monks. The top worldwide GR clears in non-season) era 11 in comparison to era 12 have increased 9 GRs, 12 GRs, and 7 GRs, respectively, for these classes.
Logically, if the new AoV set/build was buffed to be equal to or close to the GR potential of the best prior crusader build, do you honestly think it would dominate the leaderboard to the degree it is now? Stated a different way: If you were pushing the leaderboard, would it be in your best interest to push the build that can clear a GR 150 in non-season or the build that can clear GR 138?
I have been reading recently about why people ignore facts/confirmation bias/motivated reasoning/backfire effect/evolutionary constraints on our thinking about needing to be social versus analytical. This could be an interesting read.
We could look here for lots of metrics that consider relative class strengths from era 11 and era 12.
@Negator,
I am still waiting to see if your data analysis is season or non-season?