I have slightly different observations:
(1) I think some of the reduction in the top average earners has to do with the price of Steem being lower.
(2) Another thing that has changed is that minnows are not piggy-backing on trending posts as much. At it's height top trending posts were getting 1000 votes, the @brendazambran post got just over 600. Maybe low SP holders are finally cottoning on that whilst piling votes onto an already popular posts benefits the author. It doesn't give them much in terms of curation rewards.
I must confess, I haven't been paying much attention to whales recently so they may have changed their strategy. I do hope they do pay a bit more attention to good quality niche authors. However I also hope they continue to reward newcomers that bring value to the platform too.
As for whale bots that upvote based on author lists... they are a law unto themselves!
I started working on a tool that will help whales find good content based on dolphin vote momentum. That is how I noticed the shift. Its not like they switched 100%, but its noticeable.
Great - your tool sounds interesting. It would be great to see it once it's done.
I will release it as a web app for everyone.
I need that tool, like right now! I've been really having a hard time finding new authors that I love.....I know they are there, but it takes too much time! thanks in advance for doing this.
I forgot to address your 1. point. The lower Steem price has been partially offset by an increase in the daily rewards pool.