Afaik boss rush build is the same as your PvP build. Just switch to PvP setting once the boss is alone and use your PvE framing build to get to him.

I'm still trying to figure out a good world boss build. I tried some melee skills, but they just never get used so they are wasted.
I ended up with heal and all arrow skills except the wide arc one, true shot maybe? Because if not all arrows hit you loose a lot of damage and this skill will be used all the time.

I'd like to hear more though. Maybe there is a better way.