This might be the same for other classes, but I have not played them yet. I don't see why this (and other interrupt skills?) would be on the same global cool down as everything else. The cool down on the skill alone should be enough to keep the skill from being spammed. Having to wait 2.5 seconds, or get lucky and not be casting an action just seems silly to me. They are very situational, and generally very precise timing is needed.