There are times when you will be fighting things a couple of levels higher than your character. This is easy enough for some, but others might find that they need to be a bit more careful. If you let yourself get a couple of levels ahead of the guide then this ceases to be an issue. If you look through the configuration options you’ll see a place to set your difficulty rating.
The world quests aren’t necessarily bad, but they aren’t good either. I wouldn’t mind killing five of a type of monster or fighting one particular boss a few times, but after seven or eight, it starts to wear pretty thin. But going from levels in the mid-20s can take nearly 30,000 AP, so you’ll need more than world quests if you want to get your heart up in a reasonable time.