What happens if the tax was lowered to 12 steem instead of 20?

That would probably work fine in my opinion. The number is pretty arbitrary.

So, [early miners] have been getting a bum rap all along?

I guess. I mean Steemit rigged the game so they would (and did) mine 80% of the total. So by simple math everyone else shared 20%. Not all of that was whales, as there were some smaller miners too. But there were 10 or so non-Steemit top level whales. Let's say this group shared 15%, that would be 1.5% each.

That is small enough that anyone who wanted to sell has long since sold, or decided not to sell. It isn't a near-endless supply of selling month after month the way Steemit has been (up until the past few months when they have paused, at least out of their public account).