This skill is not being used in the current meta because a lot of PVP decks consists a wide variety of dark monsters. Drawing it randomly might not be helpful in a critical moment in battle. However, this skill will help you draw cards such as Dark Necrofear in a situation where all of your three Sphere Koriboh have already been used up.
Wow, super confusing sentence. "Legendary duelists drop sometimes when you have duels against them playing such as Bandit Keith, Odion, Pegasus, Yugi, and even Ishizu." What? So play as those characters or duel against them to get the drop skill?