Originally Posted by
Tehterokkar
Barrage will start to beat Glaive Toss in single target after you push the cast time of each Barrage below 2.0 seconds.
It's simple math really. In 30 seconds, 2x GT requires 2 GCD AKA 2 seconds(as 1 GCD is 1 second) and 15 focus per cast. So in focus cost they are the same. However Barrage has a 3 second base cast time(2.4 sec for me at 25% or 10.6k rating) without CDs and since it only scales with Ranged haste and not attack speed(which is the Melee/Range 10% buff), you can only push Barrage below 2.0 seconds with Rapid Fire or Bloodlust(For me with Rapid Fire it's 1.7 seconds).
Therefore Barrage takes longer to execute by .4 seconds every cycle not counting Rapid Fires/Bloodlust. However I am not sure how many of these hasted Barrages do you need on average in a fight for Barrage to be worth it over GT. But the amount haste needed(50% unbuff) is not reachable without sacrificing Agility greatly for a measly benefit of having Barrage win over GT in single target.