I think that Darius skins with changed VFX are disappointing
His passive bloodstacks is never changed in any skin. It doesn't make much sense in Bioforge and Woad King, where the other ability effects are themed green and blue respectively.
It's probably the biggest dealbreaker I can think of revolving those skins, and that may be one of those clarity things, but at this point where passive procs change in size and color depending on the skin, I don't think that it's something that should still be unchanged. I mean, they even changed Dragonslayer Braum's passive proc into the shape of a dragon when El Tigre Braum was released, something they couldn't do before because they were so much about clarification. Now that Darius has become a juggernaut, a very recent update, I think that fixing his passive for his skins is past due.