GOG has Bastion, Transistor, and Bombshell that go in this direction, but they are not big on loot.

GOG also has Hellpoint, currently on sale, although more of a 'soulsborn' game:
https://www.gog.com/game/hellpoint

There are also Technomancer and Mars: War Logs.

There was an overambitious futuristic ARPG a decade ago named Hellgate:London. Unfortunately there seems to be only a lazily fixed version available on Steam right now.

On Steam, there is also the game 'I shall remain', which is a ARPG set in some 1950s zombie apocalypse or so. Generally, there is surprisingly little in the wake of a Diablo style scifi ARPG.

Thanks for all the tips! Warhammer 40k: Inquisitor looks most interesting and most Diabloesque.

Greed: Black Border

if your interested in a co-op play i might want to give it a go too... i'm crouching ahead alone ;-)

Just Google'd the game, the 3rd result was: "Space Siege - Endless Boredom in Space"
Didn't leave a good impression at it seems. What a bummer.

And it looks like no one mentioned Space Hack. There really needs to be more Diablo in space.

How much RPG and how much Sci-Fi do you need? Cause there's a bunch of Japanese developed games that like to disguise themselves as very RPG or very fantasy, but then pull off their mask like Lupin.