Game went through closed Beta, Open Beta. Difficulty was increased in Open Beta already. Game is easier in solo mode, its intended. If you want increased difficulty do quests in groups and for the love of Kahn stop this whining already.
If your point is that they tested extensively, then let me say that changing the difficulty DRASTICALLY within the last days of open beta, a few days before launch, without additional testing afterwards is the exact opposite of extensive testing.