I'm not exactly sure if the event is functioning as planned. At the moment, Stormwind is absolutely overrun with ghouls which are rampaging through the streets and slaughtering everything that moves. The auction house, sellers, and even the lender are all unusable--that might be frustrating for players who, once the event is really live, are only trying to go about their day to day business.
Over on the WoW subreddit, players have also found ways to bring the zombie infestation out of capital cities, making entire regions of Azeroth uninhabitable.