At the time, the vampire only had a third of his power left, if I'm not mistaken. But yes, I understand and agree with you. The power scales are currently very confusing in POMA.
I mean, even Long Chen, who in Danger Zone had the Internal Energy of a Xiantian, didn't look as impressive as some of the ocs. The MC who was a MH at the time was able to withstand a blow from him even without the Golden Seed and still land a hit that blew his head off.
Of course, I know it's said that he beat everyone relying on his regeneration, but he should still be strong on his own.
Edit: If I'm not mistaken, in He Mei's POV, she says that in the past LC only beat the vampire because the crazy man didn't get tired and regenerated constantly.