User blog comment:Saratje/IMPORTANT : Warning to MOD (modificaton) making + Dawnguard./@comment-4787430-20120807172942

Really, it was under my impression that the Dawnguard.esm is required to be checked along with the Skyrim.esm in order to load a modification that uses meshes from Dawnguard. So, that would mean it would only load the modded Dawnguard Armor piece if Dawnguard is present. At least that is the way it's been with other DLCs. I don't have anything from Dawnguard modded, but I will test this out to verify if the Dawnguard.esm is or isn't required to load.