I like the random rule as well and don't really see the need to change it.

I would actually like to see rules shift around regions though rather than be static. With this it would be nice if the presence of certain rules lowered or increased the chance of a card drop. For example the presence of the plus rule would slightly lower drop rates since this rule generally increases win rate while 'difficult' rules like random or chaos would increase the drop rate of cards. Might be worth your while to take on certain NPCs when they are playing under the more difficult rules.