Usable for grinding = not fail hard, can win consistently.
Original = original.
We understand that there are specific combination of cards which can grind faster. Or give higher winrate. But what we mean by usable for grinding, is the kind of decks you're going to use for quite a while, not just "make, try, forget" decks.
Of course, compared to Wrecking Ball, for example, these decks will fall behind, but not that far. So still usable.
About originality, we do tried our best to make original decks, but people can of course see them differently.