Hmm... so it seems that the warp trick still works, but the head piece drop isn't 100% if you use it.
In exchange for the loss of data after clearing Floor 100 during the Assault mission “Nyzul Isle Investigation”, the chance for obtaining the armor pieces has been increased to 100%.
Has anyone who has a runic key tried doing any lower floor boss runs with it? I'm still convinced that SE's statement is ambiguously worded and could possibly mean that armor drops will be 100% on all floors the 2nd time through, assuming the runic key holder is the disc holder again.