IMO, HS and DGQB probably existed around the same time, just that their appearances in wulin are different.
When HS was fighting against the Ming Sect along with other sects, DGQB probably only beated a little amount of peole and wasn't famous enough to be known by HS(also because HS doesn't belong to wulin and doesn't know any events that took place in wulin). Probably one of the reason why young DGQB couldn't any one to lose to because HS kill them all already
jkjk. HS took like a 40 year break from wulin to invent his 9 Yin, during this time I guess DGQB was beginning to give himself a name in wulin. I think he retried in his late 40s, so when he retire, HS just return to wulin.
also being call Demonic Sword, DGQB's reputation isn't really good with the people and was forgotten really easily(even his name is quite arrogant). I think this is the same with RWX,(correct me if I'm wrong), I remember that LHC doesn't even know who RWX is and it was just been 12 years. I think it also goes the same to HS, no one wanted to mention some great martial artist that kill almost everyone in wulin. that is why his name was forgotten, until someone found 9 Yin.