Scion Deck is ridiculous. 100% win ratio on the Imperial. Definitely the go to GMP farm team. Primals are good also but they have very moderate stats and can't easily beat themselves.

As to someone's comment earlier, I'm believe they're is some AI learning. Several strategies on many difference NPCs that would give me a solid 20+ win streak will randomly get shut down (by nearly the same card every single time) and never work again until different cards are used. Least this is what I noticed on the Imperial, Rhiki, and the Hearts NPC in Golden Saucer.