Blurred frenzy not interrupting current animation?
GW2 uses a sort of Queue system for skills hit in rapid succession. Only surefire way to cancel a skill to do a new one is dodging/movement. Not sure if any skills immediately cast and interrupt other skills but could be wrong about that.
I think there is also a finishing animation after the execution time in which case the skill is already activated. So there is some small delay. The queue system is from GW1 and if I remember correctly you could interrupt animation for auto attack but here the auto attack is skill #1 which might be part of the issue (my issue ).