When the Dark Portal threatened to open and Highlord Kruul menaced Azeroth's cities, I was all over it. My guildmates and I raced from city to city trying to find and destroy him. We could not wait to walk the shattered soil of Outland. Similarly, when the zombie plague descended upon the cities of Azeroth, unleashing armies of walking dead upon our streets, I was once again to be found gleefully hacking down this new threat in out of the way places. Technically, that was the second time the undead had flooded the world, the first time being when Naxxramas-40 debuted, and I remember being excited about that, too.
Heck, I was even excited for the first elemental invasions. I farmed Avalanchion for quite some time for a shield I replaced the next day, as I recall.
So basically, as an adventuring sort in the World of Warcraft, I tend to be excited when there are doomsday cults preaching the end of the world. That's steady work for us hero types! I say bring on the chaos, the despair, the waves of elementals lurching out of rifts, the cults spreading fear and treachery. How about you?