The problem with your tests is that your melee swings can skew the results. What we really need to see is how the proc works on the Isolated ability. You can achieve this by turning your character sideways since the window you can auto attack a target is smaller than the window you can use special abilities.
If someone would like to take the time to wait for a shout to come up and use that rage for 1000 BT's then they can go ahead. Thats the only way I can see you being able to run that test.