There is a good chance that sin eaters have occurred in minor manifestations on other worlds, nothing anywhere near as prevalent as on the First though of course. Ascian involvement makes it very plausible that the Ampadori were set up with visions of sin eaters to promote the mage wars. This all makes sense.

That said, it seems clear there is still an awful lot we don't know about Ampador and Mhachi. I'm rather hoping that we get more information about it because as far as we've seen there has only been one of the lion sin eaters, and the Ampadori recreated it exactly. We've only seen the one, which makes it appear to be either exceptionally rare or even unique. As we don't know how sin eaters choose the forms they take when they are initially corrupted and transformed, we're left with the question, did the Ampadori see this lion in particular or have there been others on other worlds?

An answer to that question alone would answer many others, including whether they were able to peer into the future or not.