I am fairly certain this is right but would it be useful to keep the apocrean weapons with the regular versions, or in short using the Obsidian to poison and using the regular for damage (seeing as an Acheron does more damage vs a strongly poisoned foe than an Obsidian edge)?
The Obsidian Edge/Acheron seems like a good combo
Obsidian carbine/Sentenza would be great against gremlins as both have same shadow damage, vs slime both would be equal, (though Sentenza would be better in poison gremlin/slime levels since OC cant poison them and Sentenza has a gremlin boost)
Obsidian crusher/Graviton Vortex seems inefficient (and besides vortexes aren't meant for damage they are to clump enemies for your brandish teammates, thus the Crusher would be better)
Except that Acheron will kill the enemy in one charge, and Obsidian Edge might leave it alive. It's not worth a subpar charge just to poison when you can throw a solid, one shot one that obliterates everything, including Undead.
Ditto with the other weapons. Plus, are you really going to craft a Sentenza when you have a Carbine?