This probably won't get seen but I did want to leave my 2 cents. I respect Morello a lot and I am excited for Darius. But I also have to agree with the OP in a way.
When I laid eyes on the sneak peek for Darius the terms "blood knight", "black knight", or "berserker" did not come to mind. No, what I first thought was that it was a living sion legendary skin. I can't help but explain the feeling of what I think his problem is is reverse omen syndrome.
Think about it... Omen was cancelled because his design was too specifically uniquely niched and it came out all wrong. Darius on the other hand came out too 'right' because his design was too generic.
What differentiates Omen from a jungle mob? Well, what differentiates Darius from any other soldier? To me that's all he looks.
I suppose it would be worth pointing out that Riven pretty much suffered from the same thing, except Riot actually fleshed her out by giving her a tiny ass body and a broken sword (which was their stupidest design yet IMO, and I still despise auto attacking with Riven because it "feels" weak to do it) but nevertheless it made Riven different. Darius doesn't even have a distinguishing feature, even Garen has his Long-scarf-of-badassness.
The final flaw I feel is the release timing. No one is overly hyped anymore because we've now had 3 late champs in a row on irregular patching schedules. And to add insult to that injury we know because of your red post last week (regarding future skin releases with champ releases) that he's only gonna have 1 skin, and everyone knows it will be Crimson Elite.
This doesn't mean he's going to be unfun or bad. His kit looks downright fun as hell. If only the character felt the same way to me :/
PS- I love Riven's voice, story, and playstyle. I just despise her classic skin and broken sword, it makes her feel "bland plus a gimmick"
PPS- I typed this from a 3DS, plz excuse spelling errors, my hand is so cramped right now :X