Thats true actually, havent thought about it yet...I will try it out (though i think the result is clear)

*Build Updated*

;D

Seems pretty solid build-wise. Your guide is detailed enough as well, and fairly informative. +1 from me.

I will say, though, that I feel you would benefit more from a Randuin's Omen than Thornmail. It would help your team out a lot more and be more useful in teamfights. Most likely you'll never be focused enough for Thornmail to be that useful. Even Warden's Mail would be more useful. Not to mention RO will give you more AD with Atma's Impaler.

Cheers mate!
Check out my guides if you have the time. :)