i didn't founded him really tougth.
just hit him in neck when he shakes his tail. beware of his acid throwing, cause it will it you lot and erase your stamina.
when he don't shake his tail but yourself on his side, or behind him cause it could hit with toung.
when he is 40% left of health, you can cut his tail, and then it's really easy cause he can't hide anymore (visible every time)