I recently used my control shaman against Zoo. I took him down to literally 0 cards in hand and 0 cards in his library. Literally. He never ran out of steam until he had no more cards. Is that how you're suppose to win against Zoo now?
So yeah, the more people play Zoo and rush the more other people feel compelled to play it. If that's not the very definition of cancer (a disease that spreads to other parts of the body) then I don't know what.