Well, this popped up a while ago on Reddit, and I've waited for a long time but no one cared to re-do the chart. And since there are now approximately 23 threads per minute asking those questions, I thought I'd just give it a go. So here's the somewhat updated difficulty overview:
Disclaimer: Many of the values are guesstimates - solid guesstimates based on lots of work, but not exact science. In GR key drop rate and some T11-T13 data, like DP drop rate, could always benefit from more data.
I've been working on this project for quite some time, and have just finished the main features I intended to add. I still have a couple things in mind so I'll likely keep updating it in the near future.