Damn, the sub is quite strong in this one. The mixing is actually pretty solid; however, the drums could definitely benefit from some more compression since they seem to battle with the sub for prominence a little. The kicks have a lot of mid, which can be fine, but the most important parts are the transient (click) and the bass). The guitar is excellent though.
I know that deathstep is generally super repetitive, but given the high frequencies of the basses, I think the high screech patch could use some more automation or LFO manipulation of some kind to keep the patch interesting throughout the drop (it will reduce the 'atonal-ness' of it just enough to 'wow' the listener. The second drop is good though; that long bass works well.
Also an important note, since you implemented a 1/4 drum beat for the third drop, the death step drum may not be the best for that section since it has a really long reverb tail. That can quickly clutter the mix when kicks are coming in at such a fast pace. (I.E. use short tailed snare/clap samples, or just go with kicks and cymbals for that part).
Lastly, the ending could really use some form of an outro, at least more than just the beat suddenly ending. Honestly even a simple impact would do the trick, haha. The reverb on its own sounds too empty.
Overall, that's quite a heavy hitter!
Keep it up,
- False South