Two changes (either one or both) would make this rule far more "fair" when playing vs NPCs:

1. Give the NPCs more card in their collection. If they have multiple 2+ cards in their deck, give them at least 10 1*-2* cards in addition to their best 5. If they have multiple 3+ cards in their deck, give them at least 20 1*-2* cards in their deck in addition to their normal 3+ cards.

2. When randomizing your deck, one card is randomly chosen from your highest tier of cards (so if you had only 1 5* card, it would always be in the deck). The rest are chosen randomly from the highest tier you can use (so, all ** cards if you have 30-59 in your collection). This way your deck isn't weaker because of the Random rule, but it's still random.

Having change #2 in place for PvP matches would also balance things out, rather than having them be totally arbitrary. That way, you don't get a match where two people with the same collection are playing vs each other, and one has 5 * cards while the other has 4 ** and a *****.