I don't see how lowering the difficulty to Hard fixes PotD's problems.
By not swarming the player with as many enemies, which only increase the dificullty by brute force - by more enemy characters' recovery timers and actions for the player to worry about.
it will remove the last remaining shred of challenge from everything but the megabosses.
Those fights "felt right."
Ultimately the problem stems from the fact that we are playing pre-defined encounters where the variable is the player with his tactics, party composition and degree to which he takes advantage of his party's abilities and synergies, and takes advantage of game metaknowledge.
Due to the same fact, any particular encounter's difficulty is very much in the player's hands, regardless of the difficulty setting. Of course, on Hard or PotD it would "easier to achieve the feeling of difficult", because you would be to a bigger extent forced to make the optimal/rational choices.
However, wouldn't you agree that, with enough preparation and metagaming, it is possible to have an easier combat encounter on PotD than you would have with the same encounter but with a less rational "roleplayer" behavior on Hard?
What I've said I don't like about PotD is the way in which it increases difficulty - by buffing and increasing numbers of enemies, instead of making their behavior smarter. I know - who did ever do anything more than that - buff and increase numbers of enemies? But still, I regret it.