For DPS classes, Wrath of the Lich King was a numbers game. In that - How high can the DPS meters go, for real? Heroics became races against time; and, toward the end, Icecrown Citadel became Recount’s favorite battleground.
Cataclysm, however, is not about this race for the Champions of the DPS Meter. No. Cataclysm is about “How can I best help my party, stay alive, and then put out the DPS numbers I am meant to?” If you can best help your party by running away from the boss and not actually doing damage in order to stay alive and live to Mind Flay 20 seconds from now, you had best do this. The DPS meters will wait for your triumphant return.
From my casual observation, Cataclysm has brought back the importance of Group Cohesion; how best may we work together as a team? What with guild achievements and guild building, WoW has really become a game of working together rather than apart. Allegiances are being formed within guilds, and guilds are coming together to overcome hilarious odds, all for the sake of being together.
This transfers over to Heroics and Raids, where the team must best work together to their greatest strengths and advantages, which means blowing your cooldowns; using your trinkets; and crowd controlling where necessary. Abilities long lost to the land of Vanilla WoW have pushed their way into the limelight again, and players are beginning to realize their usefulness.
It is not that the game has become more difficult; it is that the game has fundamentally changed. And this change is good! However, as change is, it takes some getting used to. We may not be able to overcome every new obstacle on our first try, but with a bit of ingenuity and learning, we will eventually strategize our way out of it, or further into the dungeon.