At some point in the not too distance past I saw someone post a neat little chart for game difficulty with, I believe, Villains adding a number like 2 or 3 and environments adding a little as well, while particular heroes might not modify the number at all or be worth negative (by making it easier).
I tried searching for it but have not been succesful.
Does anyone know where this is?
Is this what you're looking for?
http://x.gray.org/sentinels-of-the-multiverse-difficulty-scores.html
It doesn't look entirely different than that, but the numbers were much smaller. A condensed version, I suppose?
Try looking through the statistics project thread. That’s where it would be
My intuition is that it was posted to BGG.
Definitely BGG. Don't have the link handy because I already printed them out for myself and my ususul group.
If I find it before my break's over I'll edit in the link.
Turns out it was this:
https://greaterthangames.com/sites/default/files/forum/attachments/SotM%20Difficulty%20Guide%20Tables.pdf
Okay class, let's all review the tables so that we can argue about how they're wrong....
No arguement … they're all wrong. 
It is based of the statistics table, which means it isn't wrong so much as a misapplication of statistics.
I was referring not to the question of statistics's value, but to our habit of arguing endlessly over everything ("Bunker needs fixing", "Mr. Fixer is low-tier", etc).