They did a good job with the Dungeon and Hell feels pitiful by comparison.
Given that to open Shadow Chests you need the Shadow Key from the dungeon it implies it should be harder but it just isn't. There really doesn't seem to be much down there either. Short of a large number of Obs/Hell brick houses with a small number of chests in the central region there doesn't seem to be anything there. Once you get to the regions outside of the centre I barely saw a single house and certainly no chests so there really isn't any reason to go back down there.
Given that to open Shadow Chests you need the Shadow Key from the dungeon it implies it should be harder but it just isn't. There really doesn't seem to be much down there either. Short of a large number of Obs/Hell brick houses with a small number of chests in the central region there doesn't seem to be anything there. Once you get to the regions outside of the centre I barely saw a single house and certainly no chests so there really isn't any reason to go back down there.