Hey @themarkymark,
I ran the numbers across November (excluding those with beneficiaries). I get 18.1% on average. So clearly not 25%, but higher than the SteemDB number (I'm not sure why this is so low).
We can assume larger whales and popular posts curation rewards will be less than smaller authors with fewer votes.
Yes. For popular authors the ratio drops off quite a lot.
For posts with higher payouts there is also a drop off in ratio, but less marked. I guess high payout posts are a mix of popular author posts and surprise hidden gems coming to light (like with curie).
18% has always been the number I've gone off. When I checked around 100 posts, I was around more like 16%, but if you took entire Steem probably closer to 18%.