I'm liking your steps so far! I feel the strongest is the blue colored one on the in the bottom right hand corner, mostly because of the asymmetry. Asymmetry was a problem I feel I was having myself.
I think one of the things to address is it doesn't particularly come off as Darksiders style. Looking back at the provided images, there were a whole bunch of crazy, elaborate, and gnarly shapes which really make the weapon stand out. So I think you could definitely take the design and boost it that way. Try looking at some of the references and see if any ideas from there are helpful.
I'm looking forward to the 3D version; you're definitely taking a different direction from the conventional pieces everyone's been making, which could be cool! Aside from that, let's go AiP!