As some of us know, there have been people running damage tests in lockdown. One of the test results shows how little defense actually does for you. The post can be viewed here: http://forums.spiralknights.com/en/node/63022#comment-520148
For an idea on how defense works in PVE, read here: http://wiki.spiralknights.com/User:Antistone#Effects_of_Defense
Comparing the two, defense does a whole lot more for you in PVE, the difference is flat out obvious.
I don't know if this is a bug, but it might be. That's why the post is here in general discussion. Nonetheless, defense should do more. After thinking about it, it's strange how toothpicks are so prevalent despite how prevalent skolver is. You'd think with all that pierce defense that something else would be used a lot more.
It is weird that it has very little use. Would be nice if defense actually meant something in LD. We could maybe, possibly get a little more variety.