Design style is different too.
Diablo I & II = takes place in a defined dark, Gothic fantasy atmosphere although almost all weapons, armor, and architecture is done with realistic sensibilities. (Ex. : A spear looks like a spear, not OMGWTFBBGSKULLDRAGONEATINGAFLAMINGSPIKE DOING 2,300.76 DPS WHILE BEING ONE-HANDED!1!!1!eleven!)
WoW = Spikes, over-sized shoulder armor, skulls, flaming skulls, bright flashy colors, EVERYTHING TURNED UP TO FUCKING ELEVEN TO FIT THE SENSIBILITIES OF TEN YEAR OLDS, and having absolutely no idea how to create a Gothic atmosphere without over-doing it (Ex. : a slightly darker pallete swap of a OMGWTFBBGSKULLDRAGONEATINGAFLAMINGSPIKE DOING 2,300.76 DPS WHILE BEING ONE-HANDED!1!!1!eleven!) .
Hell, I’ll still play it because I’m intrigued and because it is a Diablo sequel, but I know that there will be moments in the game where I will cringe uncontrollably.
Seriously: dual-wielding crossbows akimbo-style? God damn it, is everyone who works at Blizz completely blasted off their ass for most of the development stage on these things? I got over the fact that everything was in bright primary colors in a dungeon level and that all character models were all out of proportion and cartoony, but there’s only so far they can go with just saying “magic explains all, ‘rule of cool’ determines everything” before I have a stroke from the stupidity emanating the idea. (/rant)
TLDR; The new Diablo team has none of the sensibilities or design philosophies of the original team and made it in the same vein as World of Warcraft. It strikes a nerve.