A general difficulty -> TB amount could likely be found but I don't know it.
Just as a suggestion: Now we have to calculate the results as quick as possible as some deadlines are just a few seconds.
Why don't we just add some seconds to the deadline, just to give everyone enough time to finish processing?
And some blocks take too long. We can just add some math to reduce them!
Say: Actual deadline = (calculated_deadline ^ 0.8) + 120
10s => 126s
100s => 160s
240s => 200s
300s => 215s
1000s => 371s
3600s => 820s
This way we average at around 240s again, have some extra time for slow HDD/CPU's and avoid extra long block solving times.
If you like it I can do the math to get exactly back to 240s average.