Dawnbringer wasn't even a year ago

Yeah, and neither was SG Ahri but she still showed up in the Skin Dev Video as a possible thing to look out for this year XD So, who knows, we might see even more that already got Legendaries last year.

Meh dawnbringer is almost a year old though.

When the pulsefire skins hit live,dawnbringer will have been around ~11 months old.

Normally it would have been unacceptable but it's Pulsefire so it's forgiven.