The focus group felt that the first eleven levels of the game were well done -- immersive, fun, and rewarding with a great story. The consensus from there on out was that the rewards didn't scale to match the difficulty, leading to a situation where it was more rewarding to ignore the quests, and instead kill monsters. Since the majority of the TERA story is told through quests, it's important that they be worth doing.
This information allowed the TERA developers to go forward with a better distribution of quests, better rewards, and a lot more quests overall as part of the westernization of the game. Take a look at the full account on the TERA site for all the details.