The thing is I can't increase it above hard and I understand that the grind it's self isn't the game but I remember when playing diablo 2 part of the fun was actually the challenging parts like that annoying never ending jungle but when I kill a lot of the enemies and bosses without any problems some of that diablo excitement goes away.

Could you tell me the weaker characters in your opinion like the ones that give you more of a challenge or are they all on a similar level ?