World of Warcraft has never been a bubbly, friendly place. Most of your quest objectives require the death of all sorts of different species, people or “abominations.” But, with few exceptions (like Stitches), you’re always the “good guy,” or the heroine. There’s not much recrimination for what you’ve done. Sure, if you go at war with the Booty Bay goblins you get friendly with some pirates and they give you a hat and you get a title. That’s actually a reward for going “bad,” and goblins outside Azeroth don’t seem to really care.
What WotLK seems to focus on, intently, is guilt and consequences.
Look at your quests. Several involve torture. Many involve willing genocide, the capture of infants, or deaths of once-allies. In early quests you do what the Kirin Tor are too good for, and then you kill a sorcerer forced into service against her will, and receive a letter from a grieving parent who doesn’t know you did it.
Face it, you’ve always done “bad things” while playing WoW. You’ve killed other players over flags, you’ve killed ogres for a piece of paper they drop (ogres who call you their king, even), you’ve invaded castles and jungles and just wreaked havoc so you could get some gold or gear or sometimes save the world (not necessarily a bad thing). You’ve decimated the populations of entire species for achievements and Nessginwary.
WoW is just finally making you notice that maybe, just maybe, what you’re doing may not always be okay. That you might not always be in the right, and you can’t always be the hero. Not even a paladin’s armor comes out untarnished, nor a priest’s. Everywhere there is genocide, racism, mistaken identities, dirty secrets and righteous causes that have terrible costs.
I have not yet experienced the culling of Stratholme, so I cannot speak for it. But from what I have experienced so far, WoW has stripped away the shiny veneer of the quintessential “hero” with a heavy application of guilt and bloodshed. It’s much more real now that your actions have heavier consequences than simply a frown or an “oops.”