Disregarding the difficulty (which I agree is too great)... the biggest "FU" to players if the lack of good new rewards and the fact that gold payouts are HALF or less of what Underworld provides. And.. there's not a single good "Gain XP and Gold" farmable battle since all the "bosses" are placed 1 battle levels. It's as if they specifically designed it to NOT forward player progress. Once complete, if you don't need Nightmare or Ruin talismans, there's absolutely no reason to ever visit it again.