Earlier quoted context omitted.
I don't feel like this is a good application of predictive networks, but maybe I'm wrong. Tiny changes in wording of a card can make or break an exploitable synergy. You can say "tigers basically look like this, ish" to an image recognizer, but you can't just say "decks that look kinda like this are super strong; decks that look kinda like that are super weak". I'd think the best approach here would be to have an age…
Magic the Gathering cards have pretty standard and predictable wording and keywords. Not sure it could understand everything, but there would be easy patterns that apply to hundreds or thousands of cards.
To add to that point, decks can be good or bad based on the ecosystem (meta) they're playing in. A deck that aims to rush you down might be great in a meta where players expect slow decks, but terrible in a meta where many decks have means of healing themselves.