Thief %/s (KMS Unlimited and GMS Tempest)

k. Updated OP.

From what I recall, Boomerang Step was said to have defense ignore in the past like Assaulter, can anyone check if this is true now, or was it always wrong?

That's never been true.

Also try using only Assassinate + Dark Sight for 1v1; I'm getting a higher value for that than for BStep+CE+Nate+DS+FH+5KP.