The power increase between easy and normal dungeons is HUGE. Easy is way to Easy after hitting 100+ gear score, and Normal is ALWAYS difficult as it increases to match every level.
Easy is intended to be the difficulty that the dungeon is encountered during story mode. Normal scales with your level, and yes, it’s pretty much impossible to complete dungeons on “Normal” once you hit the 2nd or 3rd dungeon, and stays that way until you get close to completing the story. Unless you get really lucky with your spell drops.
My favorite is when easy is the same as normal, which happens when your current level and the dungeon level are the same.
I think that this is one of those things that will eventually be looked at and changed at some point down the road. I think easy mode was more or less tossed in, quickly, to improve playability of dungeons, immediately.
Once bugs are sorted out, and the economy is sorted out, and various balance issues are sorted out, then they can rebalance dungeon difficulty in a more logical way.
I think the issue with the scaling difficulty is that it assumes what a gear score for your level ought to be. However, that gear score is mostly unreachable mid-game for a number of reasons. That makes normal feel more like nightmare mode because you die in one turn.