Although there were quite a number of Epic creatures like Jade Toad, and it could drop many good items, there were not many tutors in the college who were willing to kill one.
The Jade Toad was poisonous. The blood and bodily fluids that spewed out were deadly poisonous if one managed to lacerate it. Just touching a little bit of it was enough to kill someone.
Before its death, the Jade Toad would even self-destruct. Within a radius of tens of meters, the poison would spray everywhere. Touching any bit of it could result in death.
If there wasn't a special need, who would risk their lives to kill such a dimensional creature? Humans were still humans after all. Even if they had the ability to kill Jade Toads, who could guarantee that they wouldn't be distracted for a moment? If they were stained with the poison, their outcome would be dire.