I'm not entirely sure what you're looking for. I watched Beautiful Bones: Sakurako's Investigation and enjoyed it, but I'm not sure I ever thought it was "densely packed." I also watched Idaten, and kinda feel the same way.

Also might help to know what genres you prefer/avoid. And what kind of stuff you want your anime to be densely packed with. A comedy could be densely packed with jokes, but you may not want a comedy. Someone mentioned lore dumps, but you may not want that either. I had written out a list of shows, and then second guessed what it was you were really looking for.

My only suggestion at the moment, which is a bit different, is Mushi-shi. It's paced quite slowly, but it's beautiful and riveting. The slow pacing works in its favor, not against it. I can't look away. Try it out sometime.