I've noticed Darius doesn't seem as great early game armor/health wise...or at least it appears so when i play. Now i've been going for a tankier approach instead of a full out AD route. This build still gets lots of kills a game, plus keeps me tankier at the start of the game.

*NOTE* if you're fighting bruisers than by ninja tabai boots instead of merc treads
Late game i sometimes switch up Maw for a 3nd Bloodthirster and drop my merc treads for boots of mobility for speed.