*shrug* I don't really think about 6 item builds that much; your build needs to be efficient throughout, and IE/LW are still going to be things everybody wants in their build (plus a vamp scepter). Add a defensive item and now you really only have room for one more item.
This is why I always math for 2 or 3 item builds; after that, you're going for a defensive item, and you're going to spend a good 10-15 minutes with just those items (offensively). And Movement Speed is more important than you'd think. I'm pretty sure there's a thread on RoG where people are debating this.