Victor's Cache
According to the support people I talked to (who separately checked QA), the description is wrong. Victor’s Cache has “a very small chance” to drop a vision crystal; it’s not guaranteed.
The wiki, as it should, repeats the description verbatim. No one has updated it to mention the bugged text.
The Crystalline Ore is the only other guaranteed from the chest the vision crystal has a drop rate actually and is pretty random
John Smith: “you should kill monsters, because killing monsters is awesome.”