personally i would use 5X frost trap, after using formation macro to spread out my characters.

play around with it and get a good feel on how far to leave them spread out for max range.

ALso if you use keyclone, i would put scatter shot on round robin, so you can scatter shot multiple targets in a row.

This should give you a good amount of time to get ahead of them.

I only have hunters up to 12 so far and have never even pvp'd on them yet so this is all theory of course.