It would be useful to see what percentage of mobs died by which method, or that despawned. I was thinking per mob type.

This would allow for XP farms seeing which percentage died during weakening vs which percentage died due to player which hopefully would be 100%, but this would allow detecting if it is not. This would allow for fall based mob farms with magma at bottom to see what percentage die due to fall vs magma to see if height needs adjusting. It would also allow seeing what percentage of mobs despawned which could be used to see if there are any issues with a farm, or there are any mobs in the surrounding area, though there are other ways of knowing that.

this is already entirely possible with scarpet. You just make a map where you have an entry for each type of damage source, and then print it out. Again, I may work on a scarpet script as a POC to show you if you want. It is, however, entirely possible.

Ah, thanks, I didn't know that was possible with scarpet. I'll try and figure out how to use scarpet

Edit: Got a working but inelegant solution by using a scarpet script to log death reasons and a python script to parse the logs and count the causes for each mob.