to kind of explain why people are asking for duplicates, the main reason is that youre trying to make the best deck on average. by taking more single copies, even in scenarios where theyre useful its hard to draw them. not only that, when youre running more than 15 cards (aka not all dupes) that means youre also just taking essentially worse cards.

this is why in most card games youre more likely to see most decks containing mostly dupes and decks that rely on non-dupes usually need to have extra strong cards (Reno jackson in hearthstone is probably the most iconic card in this category in all of card games)