This. Bitmixer has a flat pay rate across all member ranks which sets it apart from virtually every other signature campaign out there. Bitmixer's rates are pretty OK for full members but slightly below average for senior members and definitely below average for hero members. But they are also unique in that you get paid at your own pace and they don't set a minimum number of posts in order to get paid. For some senior and hero members, it might make sense to stick with Bitmixer vs. higher paying competitors for these features alone.
I agree with you. Especially the absense of a minimum required amount of posts made this signature the right one for me. I've got weeks where I am really active, but I also got periods in which i'm busier in real life and then I do not post many posts on this forum. Together with the weekly payout this still remains a great signature campaign. However, as you already mentioned, especially for the hero members the payout is really low now in comparison with other signature campaigns.
My guess is that the Bitmixer sig campaign would be much more popular if they changed their pay rate to 0.001 BTC per post for seniors and heroes while still keeping the zero minimum post limit and automated bot and payments which is what makes this campaign currently so great. The fact that their campaign is still quite popular despite the slightly lower pay rate for these ranks means that it's probably not necessary though.
I've noticed that marco's bot looks very similar to the Bitmixer bot. I wonder if that's where he got his inspiration from.
EDIT: Just found
this thread. It seems the Bitmixer bot was actually the direct inspiration:
