Quote from RaccoonsWithBangs >>
I opened a normal Putricide from a standard rogue pack despite already having the signature and not having all the current standard rogue legendaries.
Which Standard rogue legendaries are you missing and are you sure, you didn't own them at some point and dusted them?
Duplicate protection should work as normal and count signatures as collected.
Cera'thine Fleetrunner and Find The Impostor, had Apothecary Helbrim at one point but dusted that. I don't believe I've ever owned the other 2 but who knows maybe I dusted them and don't recall. That seems to be the only explanation anyway so it's probably the case.