Lots of RNG involved I got 4 cup of ace on my stage 14 account while it took me all the way up to stage 34 to get my 4 cup of aces. Jade of Whistle seems to have a lower drop rate than cup of ace
I agree with yuei.
I made a new account, and I am over stage 30 and still did not get this either, even though I DID get this card with my older account.
I think it may be possible the game deleted this card (at a later update) in case it made parasite infestation skill to overpowered.
Been sitting at stage 38 for a while now, grinding through the characters, and I haven't got the card one time in my now 2000+ duels vs standard duelists. Fighting fire with fire is not an option for me either.