diablo III difficulty is adjustable. you can make it as hard as you like during leveling and at the endgame.

I played diablo 2 a lot when I was a kid, and really, the only hard parts were bullshit mechanics like damage immunities and iron maiden. it also had no real endgame, only mindless baalruns. ubers were only doable by a few paladin builds (with reasonable gear/effort).