The Diablo series had its origin in the early roguelikes Moria, Nethack and of course Rogue. I don't know if the Diablo developers had seen Omega by Laurence Brothers. Omega in turn was a significant influence on ADOM by Thomas Biskup. Omega came out in the mid to late 80's and I first come across it in college on one of the university's Unix mainframes. Omega didn't have character classes per se but instead had a relatively extensive guild and deity system that the player could choose from. The game also had multiple endings. The player started out as a level 1 nobody and by the end of the game could end up being the Duke of Rampart (the region's major town) or Leader of the Thieves Guild or High Priest of Odin, etc. There were something like 20 different titles the player could try to get his character's name on, many of them mutually exclusive. Kind of like a high score board but with 20 separate categories. There was a large countryside with various terrains which had multiple towns, caves/dungeons, temples, and other special places. Each guild/deity had a quest the player had to complete before the player could advance to the highest rank in the guild or religion. Like nethack, ADOM, and Rogue it is ASCII "graphics" although I think there is a tiled version out there. If you've never given these type of games a try because of lack of pretty graphics, no cool soundtrack, clunky UI, no mouse support, only runs on your grandmother's computer, etc, you really should try them for one reason: solid gameplay. It's literally the only feature they have going for them. If they were crap, nobody would hear about them 35 years later. Unfortunately, AAA game companies are very good at polishing turds of games with cool graphics and soundtracks. Or the promise of in the case of Warcraft Refunded. In earlier days, it was the cover art that lied about the game within. It's only after the gamer has spent his hard earned money on the game that he discovers after a couple of days that he bought a turd. Or worse, several months in the case of pre-orders.
The reason I bring this all up is that obscure relatively unknown gems like Omega (which I believe is open source) would be a good candidate for a remastering. So long as the gameplay is only balanced a bit and not redone or dumbed down.