From Ye Weiming's perspective, the antidote for the Yin-Yang Reconciliation attacked combined with the cure was the true treasure.
Not only could it play a crucial role in the rescue process for Duan Yu, but many a time it could even present effects far beyond any potent poison could.
As for the not too weak, not too powerful Lightning Mink, it could likely only deal with Zuo Zimu and Sikong Xuan, and would be ineffective against stronger opponents. If unleashed, it would merely serve as cannon fodder.
If the white mink was really that powerful, why didn't Zhong Wanchou and Gan Baobao use it for themselves, but kept it as a tool for their daughter's self-defense?
From Ye Weiming's perspective, the toxicity of the Lightning Mink only had some use in plot mode.