Problem is that expert dunegons are not really expert dungeons, they are just the newest dungeons avaible, they just used a fancy name, but since they end up in the normal dungeon que, they hardly fall off the normal difficulty curve.
Now if we had truly expert dungeons as a category that would be fine

Personally I wouldn't mind if they ever added Battle square boss rush extreme, where you face increasingly difficulty bosses with some random affixes but one can only dream I suppose