I made a training efficiency calculator which you can see here:

https://tibiantis-notes.github.io/distance_calculator

It can help to also read this:

https://tibiantis-notes.github.io/Melee_and_Distance

Slimes were popular back in the day but they have very low defences so are killed quick leading to high attention needed and often idle time. Many prefer monsters like minotaurs or kobolds which have better defences and last longer.

In terms of lower attack the crowbar would have a huge inpact on time taken to kill slimes.