It really depends on what you consider "worth fighting for". If it is a stat boost to make you more powerful than other players you wont find it in GW2. If you just want to show off in cities with your cool, hard to get gear, then is likely you will find that instead.
We don't know much about the difficulty of the dungeons yet, but what we do know is that each of the 8 dungeons that are available at launch have a story mode and 3 separate "paths" called explorable mode, which can be unlocked by completing the story. These "paths" are said to be considerably more challenging than the story mode. Some links you can read: GW2 wiki Dungeons, Into the Dungeons, William Fairfield on Designing the Dungeons.