You explore with your nose stuck in some walkthrough? There is plenty to do in the Forgotten Vale and lots of things to find if you can be bothered actually opening your eyes and looking. just because you do not get quest markers for them does not mean there is not lots of things to do.There was also lots you could discover in the Soul Cairn, but the scenery did make that a bit more challenging to explore, because yes it was deliberately made to look all the same. But if you explored the place thoroughly you could tell where you had been, that is one reason why there were so many soul husks spread all over the place. And there were also more enemies in the Soul Cairn than in most other places. So for an hours odd exploration with a bit of thinking, you could go home with a lot of filled soul gems and a lot of loot. As well as the interesting side quests, and extra hidden items to be found.
Most of the stuff you can do in Skyrim, you are not going to get quest markers or little hints in your journal about, and that is even more true for the DLC, where you are expected to be experienced enough to work it out for yourself. So not so much hand holding and following the convenient quest markers. If the occasional quest marker went wrong, or you failed to understand what it was telling you to do, it should not have been a problem, they are just hints after all.
Umm... my complaint isn't lack of content. My complaint is bugs and I just plain don't like the area. I don't want to go back. I didn't enjoy it. I actually like playing the thieves guild quests and dark brotherhoods over and over again but not dawnguard.
And you can't blame me for being confused when a quest marker is showing, and it's taking me to the wrong place.
I'm a casual player not some die hard exploring RPer. I don't want to spend hours exploring, or trying to get every single quest done. I'll do some, and not others.
I don't enjoy the game the same way you do. When running through most of the forgotten vale I didn't get any combat either except for the obvious places. No trolls, no monsters, no anything. And I didn't enjoy it enough to just want to run through it taking in the sights. I just wanted to be done with it, I didn't like it.