So after a long time of thinking about it, at last I got Runebound and played it last night with a friend. I have to say, we had a blast! This is precisely the game I was hoping for and really scratches that particular "D&D light" itch I was having. What I like most about the game is that it's so narrative. With the event cards and the flavour text on the challenges and encounters, it really feels like you're in a story... And that's what I was missing a bit in Descent. Now these two games are really complementing each other for me.
Now which expansion to get?