zanzarino - here's a thought. Since the game works very well with limited access to rares, maybe you should put a limit of 2 per rare card in a deck (Leaving the current 6 for normal cards) That way the game balance will be better preserved for rares being hard (Impossible, with that change) to load up 6 into a deck for and cases of someone dumping one into the system won't cause as much damage and deck focus onto that new, broken when stacked rare.

Improving card balance to deal with it could also work, but it can be nice to allow rares to be slightly stronger than normal cards -- and I think that will take a lower limit to really have function well.