Just finished the game, and I can only say that the game isn't actually that difficult as long as you get to fight where you want, instead of wherever you find the enemies. While there are some rooms that are actually quite challenging, most of the enemies you'll find are roaming around, so you can pretty much pull them one by one to a previously cleared room.
If you're playing in hard, the same system still works, but mobs will hit harder and will take longer to kill. Yet, as long as you can dance around them is alright.
However, in those rooms you can't really choose where to fight, that often involve either many enemies and a poor starting position (flanks and back exposed) or a very annoying layout (pits, mostly, but also corridors where enemies come from both sides) hard difficulty really makes the game A LOT harder. Because those situations are already quite hard to deal with in normal, mostly. And of course, enemies such as the slimes or some ranged casters are going to be a total pain in the ass.