Actual Darius Change
So, part of the reason why Darius does as much damage as he does, is his overwhelming AD steroid from Noxian Might, and his free armor penetration from his E. If you were to take these away, or tone them back, he'd do a great deal less damage, while still dealing big boy damage. If need be, swap his base damages/scalings around a bit too, and maybe give him back a bit of his attack speed while you're there. The heal is in a fine place at this point, especially now that his mana costs are higher.