Arguments for Darius needing no buffs/changes is he has roughly a 50% winrate

What? Darius' not getting buffed has absolutely nothing to do with his winrate and I've never actually seen someone use that argument. He's not getting buffed because his kit offers no counterplay whatsoever. If he's strong you can't do so much as walk near him without getting murdered and if he's weak its a 4v5. He needs a rework, he can't be buffed with his current kit.

Actually the argument I'd use is that he has a 50% win rate at low elo and drops like a rock as you go up in elo

Meaning he needs changes to be viable everywhere

I'd say his winrate has nothing to do with it. The fact that he can wreck all melee champs is the argument I'd use. If Darius gets a hold of you, might as well open the shop because you're dead.