Yeah, it doesn't really matter on normal as long as you don't kill all 9 at once outside of a circle. On heroic+ they have significantly more hp so it's quite a bit harder to kill them without switching to a full-on AE rotation. Either way, I hold onto barrage until he leaves the shield and the adds are in a circle. Even if people have blown up 2 or 3 of them already, you can usually still get off a full barrage on the last 6 or so to maximize the dps from it.
Regarding Ovale, the leftmost box is just "short cooldowns". Stuff you want to know is available but don't necessary want to use the moment it comes off cooldown. I'm not really sure why Black Arrow is in that box instead of the main rotation boxes. BA should be cast on the boss the moment it becomes available, no exceptions. I edit the hunter script to put it back where it belongs every time there's an update, and I also make an edit to the DK script that adds an extra check to use Festering Strike to extend NP just the right amount to last until the next UB is available. I can post my edited scripts if anyone else wants them.