1) Just bump up the cost of individual group or an escalating cost as you add more of the same group. (+2, +3 +4 etc.)
Actually, errata-ing the cost of cards is a TERRIBLE way to fix things. Like Boba Rick mentions, casual players will either know about changes and use them, or not and it won't effect them much however a change is implemented, but for someone who wants to go to a tournament, if you show up at a tournament and are told the abilities of the figures in your list have changed without you knowing about it, that sucks, but you can adapt, you can still play and have fun. If you show up at a tournament and are told the point cost of the figures in your list have changed without you knowing about it, you can't play. Your entire list needs to be rebuilt, which you may not have time for. You drove however far (I've heard of people driving for an hour to get to local store tourneys) just to watch other people having fun. And that will happen most every time someone goes to a tournament for the first time.