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:
...For some ideas and additional features that I may have missed check: https://bitmixer.io/signature.html
Let me know!