To recap: with houses down and PPV increasingly irrelevant, it's mattering less and less how well you do if you're not chosen to receive a rocket push since it won't affect your paycheque or card placement - "the brand is the draw" and the Brass Ring is clearly mythical. And of course, the downside payout for lower-carders is increasingly undervalued given the cost of travel, insurance, etc. remaining constant.
I think Ryback's arguement has some merit, but if wealth is wholly flattened out it may strip those who do overachieve of their desire to excel...then again, he might argue that most of the roster is at that point already. By the same token, no other sports or entertainment industry (that I know of) pays all its workers equal wages, but the successful ones have paid enough to everyone to keep even the bottom-tier folks happy - I get the impression that this isn't happening for everyone in today's WWE.
Basically, I think a lot of it is that guys are being hosed on the Network residuals, or lack thereof - Punk brought this up before he left, and he's probably not the only one. A flat fee structure for appearing on a Network video would be simple enough to pro-rate, and top guys would make more in their downside and in merch.
Failing that...given WWE's television presence it would be simplest if the workers were made members of the Screen Actors Guild, as that would compensate some gaps inherent with their status as Independent Contractors (sic).