I know the crossbones guys, I dunno, they tend to be a bit ravey, but I`ll give Darkside and Nekro a go.
There used to be a soundsystem on the free part scene years ago called Mainline, they played the hardest darkest doomcore I`ve ever heard. like, 130 bmp but so hard and doomey.
I`ve not really heard any mixes like the guys that used to play on there for ages.