I opened a signature 8 Hands card yesterday. Today I opened another set of gold packs and within 2 packs got another 2 signature 8 Hands. So now I have 3 total copies of signature 8 Hands. I also had a copy of the warrior Exarch signature, and opened another copy a few packs after the 3rd copy of 8 Hands.
Technically that is pretty crazy luck, but it also seems like a bug because I do not have ANY version of some of the legendaries, and am also missing several of the other signatures. Duplicate protection should work on signature legendaries, right?