I disagree with the others!
Furthermore, any guidance on when to use this tag will be extremely dicey. The majority of questions about individual cards get resolved using the comprehensive game rules; i.e. the real question is about the rules, not the card.
"specific card" is not a tag I search for to see if I can answer questions. But it is useful to get a feeling what the question is about, and if I am likely to go the extra mile to make an effort. True, often questions regarding specific cards can be answered with a reference to the rules, but this is because the card is part of the game!
The tag "specific card" divides all questions on the site into two categories: questions about a specific card, and questions not about a specific card. Neither of those categories is useful.
This is your personal opinion and not a fact. Counterexample: "reality-check", "science-based" and "hard-science" on Worldbuilding SE. Divides the questions on the side into 3 categories and it works good for them.
Nice quote from relevant question on meta:
Tags that no one cares about are not harmful. Removing a tag that someone cares about is harmful.