I trust that Referback performs well for affiliates who have been with them for a while.
I believe the problem is only with newcomers – the cross-trafficing/marketing has their casinos pretty-well tied up, and anyone who hasn’t had a new account signed up with them is sending them repeat traffic, and lining the pockets of affiliates who may have sent the same players to them years ago.
I don’t think the low conversion rate is due to any tinkering with stats.
It’s a waste of time for newer affiliates to market them – the casinos are very well exposed, and the odds of sending them someone “NEW”, who isn’t branded with another affiliate’s code is lower than industry average.
That’s my take on it.