I guess it's just a rare attack. His tail swipe put me at 1 hit point when I went back after upgrading my gear. It was a close one.
Anyway, update: This offensive spear guy is probably the most fun I've ever had. Beat O&S in 2 tries in offline mode, and it was such a fun fight too.
Soon I'll be getting the fork in the royal wood, and that will be awesome~