I don't understand these PvP mechanics

I worked very hard on on my character. I am not saying I should be uncontested, but I don’t understand how certain characters with similar equipment to mine that I encounter can just wipe out my HP in the blink of an eye. I am using an Element Coat Weapon crit build and really have maximized almost all my stats as comparatively possible. Yet my damage verses certain players is insignificant when the aforementioned are hitting 5-25k+ hits on me. Is there an explanation for this?