Did you collect and vault the "Spark of light" item the postmaster had before you wiped them out? I got it on my lvl 34 hunter, and thought "who knows mebbe I'll need it later." That item lets you insta-ascend a new character to lvl 25. The old guard/vet 1 requirements SHOULD be tied to your profile, not a character save. It's likely it's really lvl based. My thought is, if you got that item, and saved it, you could use it to get to lvl 25, and see if it unlocks old guard. If not, yeah - Bungie maybe needs to patch this.