Vengeful Oathkeeper has been one of those things that kind of works. As long as they do their military challenge before yours, you can generate that extra free body. But it's only got 2 strength, and it's not well supported by the rest of the deck, so what normally happens is that it isn't a position to win a conflict. The unexpectedness of it helps a bit, as does the obligatory Banzai and Fine Katana, but it's just not spectacular - there's always other cards I'd rather draw instead.
I think you may be right: leaving the influence unspent is fine for Scorpion, as they've got better quality cards in-clan than anything else Lion can sell them.