The classes in Diablo 3 are really niche and stupid.
Out of the five classes, three are magic classes, one is ranged but it may as well be a magic class, and the only 'normal' melee class is a barbarian, which is a niche class in itself.
I would much rather have preferred the stereotypical choices of knight, burglar, archer, etc.
The combat is just lights and spells flashing all over the screen, which is the plague of most new RPG/MMO games. I miss games with realistic weapons and hacking and slashing, instead of flashing lights.
They also tried too hard to make it super 'epic' to the point of cheesiness.
The auction house feature should never have been introduced to Diablo.
And to top it all off, the multilayer is done so poorly that it may as well have been a single player game, with internet connection only necessary for PvP.