Why not replace night slash on the standard set with Swords Dance? It isn't great but sd pursuit ohkoes starting after Rocks (without starting switching out and I haven't tested without rocks) and it ohkoes tyranitar with low kick even with whatever that berry is called that weakens fighting movesThe tiering for DPP locked after the gen ended which is why its still listed as OU. Also, low usage does not mean a mon is unexplored. Nobody's experimenting with it because it suffers from having pitiful STAB options which lead to hit hitting like a wet napkin, that along with a rocks weakness and its fragility it makes for a very underwhelming setup sweeper. It has pursuit but is also severely outclassed by other pursuit users.