IMO, it really boils down to there not being enough rewards in the reward pool to go around. Even if the 'whales' were not the one choosing the posts, then you would probably just end up with a popularity contest. People like Justin Bieber, Brittany Spears, etc. would be getting massive followings (like you said in your post) and then people would just switch to who they were complaining about.
There is about 7k in rewards to be paid out each day (with current prices). That includes curation rewards as part of the payout. Even with 1,000 active users posting decent content, that's only about $7 per person.
I think having Zipf's law less drastic could result in better engagement. I'm in no way in favor of some totally equal system. What I have noticed is that the drastic curve doesn't mesh with human emotion. If a site carries too much of a negative cognitive load, it's not going to work. It really is that simple. Humans operate on an emotional basis.