Most dice based RPGs run on some sort of Dice+Modifier system. While the dice provide the probability, the Modifier is determined by the player. This modifier tends to be static which means that games boil down to grinding out enough experience points to raise the Modifier (as a huge simplification).
What has always bothered me was the set modifier. What if somehow you could compensate for a bad roll? Mulling over this problem a few years ago lead me to create a system I called Pocket, but I could never quite get to run the way I hoped. I was using poker rules as a basis (which has since been done much better with Deadlands), but I think I can salvage something by limiting the cards in play and simplifying some of the rules. The decision to continue to use cards rather than dice is practical rather than stylistic; it is simply harder to fake a card value than it is to conveniently nudge a dice roll. There is actually nothing that would prevent a trusting GM from using d12s.