Crate Entertainment first announced Grim Dawn, a Diablo-like RPG using Titan Quest's engine, in January 2010. Two years later, they collected over half a million dollars with a successful Kickstarter campaign, and later put the game on Early Access in 2013. Now, after half a dozen years, Grim Dawn is getting released. Mechanics-wise, Grim Dawn should be familiar to you if you've played any of the Diablos, any of the Torchlights, Path of Exile or, especially, Titan Quest. You go through a four-act campaign on varying difficulty levels in a Victorian-inspired, grim world, solving quests and slaughtering everything in your way. Since this game comes from Titan Quest's developers, similarly to that game, you only create a male or female character at the start, and decide on a class while playing.
Another aspect that's similar to Titan Quest is the game's class system. Like in Titan Quest, you have several masteries -- that is, classes -- to pick from. Above is the skill tree of the Arcanist, the game's mage archetype, taken from this calculator here. You have your active skills as squares, passive skills as circles and a general stat-increasing Mastery meter on the bottom. Later on in the game, you can also dual-class into something like a fighter-mage or a mage-summoner.
On top of all that, the game also comes with built-in co-op multiplayer and modding tools promised post-launch. It's the full package, pretty much: the dream Diablo clone.
If you're interested, look for the full version of Grim Dawn here on Steam this Thursday.