D-ROCK: In regards to your 3rd paragraph I own all those games you mentioned. Nox, and Darkstone, Torchlight here on GOG as well as Steam. Titan Quest on Steam. I still really have not delved deep into those because of my tremendous backlog. I figured since I love the ARPG genre and heard so many good things about the Diablo frnachise, that I decided to buy a Diablo game and see what all the rage is. It is the Godfather of ARPG.
Diablo is a great place to start, probably the best place. I didn't want to scare you away from the other games, in fact NOX is refreshingly different from Diablo so it won't let you down by comparison. I'm a bit partial to NOX so don't take my word on it but the game has a very dedicated cult following so it's not just me toting one of my personal favorites.
Darkstone hasn't aged too well but I still enjoyed it moderately, just not enough to play it more than once. Diablo 2 on the other hand I played many many times with all the characters. It starts to become repetitive after a couple playthroughs especially if you take the same character through multiple difficulty levels. Best to take a break from the game then, that's what I'm doing. No more Diablo for a while.
I even tried Torchlight as a sort of alternative anti-withdrawal symptoms drug but I strongly disliked the game, it just has no soul, so bland. Give it a try by all means but don't expect it to be anywhere as engaging as Diablo. I was let down by Titan Quest as well, it's an excellent game and one of the best in the genre so I recommend you try that one next (assuming you haven't already started to play) but aside from the gorgeous graphics which aged well, it felt rather lackluster. I only played one character and completed one difficulty and quit the game after that where as in Diablo I hit new game immediately whenever I finish the game. It's odd but I'm sure many people would say the same.