Ah, so this was the deck I asked to see. Yes, Vampires are very vulnerable to Antimatter, but only creatures with the Vampire ability actually do damage to their owner with Antimatter; maybe thats where the problem lay. All other creatures simply heal the opponent and do nothing else, hence why Antimatter isn't broken. Yes, your deck is highly susceptible to Antimatter, but even then, jmizzle posted a good solution. Antimatter's cost is high; if you can deny that for at least a while, you've done well.