Atma's is cost effective if you effectively use crit%, which most of people stacking didnt. Another thing I found out playing Lee Sin is that many of those "bad lategame" bruisers are incredibly powerful late if they build IE+Atma's along with hp/defensive items.
That being said, I see no reason for OP to build Atma's over Ghostblade since he doesnt build HP, thus he doesnt get a lot out of that one slot.
I don't see a problem with the Bulwark/IE part. The rest? Why not build a Ghostblade/Black Cleaver/Randuin's/Guardian Angel/Frozen Mallet?
Idunno. It's like, yeah. You'll beat anyone 1v1, but you'll get wrecked in teamfights. Why not build slightly more tanky with a Randuin's instead of an Atma's, and a Ghostblade or Black Cleaver instead of the PD? Then you still deal a crapton of damage (almost as much, with the Armor Pen), while being even tankier. Plus it's cheaper. --- If there's anything more important than my ego around, I want it caught and shot now.