I have yet to find a macro that can keep good up time on barbed shot until you reach the point were you have enough procs to basically spam it. If you have low crit/haste it can result in less barbed shot procs. The Bow from skit can also help with reducing the cd on barbed shot.
There might be a way by nesting the macro and setting a pause to say 5 sec. The problem I foresee is that you would waste procs by not casting them and if the macro goes to the next spell instead of barbed shot you won’t be able to cast it again until the 10 sec mark. You would have to find the sweet spot that works for your gear and ms settings and it wouldn’t work as well for anyone else.
I have 30 world ms and set AHK to 70 ms with the macro settings also at 70ms.
This thread has a lot of information on nesting the pause wait features.