Diablo is indeed the answer! Diablo 3 to be specific. The missing character is the witch doctor (for whom i didn't found a miniature that I considered a good representation of the character). But I added the amazon from diablo 2.
I wrote up a bunch of rules to make the game feel more like diablo. Elite mobs with randomly assigned affixes and loot tables where the rarity impacts the number of special properties (of course also randomly rolled) it has.
Here are some pictures from my first campaign game:

For my party of heroes I decided for the barbarian Ordue, the demon hunter fiona, and my favorite class and miniature (and therefore somewhat of a main character for the campaign) the crusader Isabella. After following the fallen star, their first mission is to reach the town of tristram, which is beleaguered by all manner of zombies. They'll be starting in the bottom left corner and have to get behind the barricades in the upper left corner.

Luckily one of the first monster cards I drew was the scenario event. Which meant that captain Rumsfeld and an archer of the tristram militia appeared, ready to defend the barricade and support the heroes.

A walking torso ambushed Isabella from under the overturned wagon. Normally having just an DL of 4, I gave them the ambusher (2) rule, which gave the undead fiend an additional +2 when ambushing. So his DL went up to a more threatening 8. Despite that, Isabella had no problem of crushing his rotting skull under her heavy steel armoured boots.
Slowly but surely the party fought its way through the spawning undead towards their goal.

The "things could get worse" card triggered the arrival of an elite mob. They have a +2 DL and an additional hp per player (+1 in this case). I rolled the nightmarish affix, which meant that every time the horde activates, every hero within 4" has to make a WIL roll against the DL of the horde and move 4" away if they fail. This was actually quite frightening indeed, because it meant that anytime a character engaged in melee with the horde fails his WIL roll, he suffers a free hack. But my heroes rolled good WIL rolls and managed to dispatch the horde quickly. Ordue's battleaxe, dealing 2 DMG on a hit, proved especially useful. Killing the elite mob gained every character one bonus exp and Isabella got a lucky roll on the loot table and managed to get a chestplate of vitality, increasing her hit points by 1.

The heroes finally managed to get behind the barricades. But just moments later the illusion of security provided by the flimsy defences shattered, as hordes of undead, spewed out by the wretched mothers, swarmed towards the town of tristram. Will our heroes be able to hold the line against the undead assault? Will they manage to eliminate the wretched mothers and thereby reducing the thread to the survivors of tristram?
The next Game will show.