I do agree it would be more useful if the response time on it was faster. There are definitely a good 33% of cases where I'm like "too late to use it, won't work if I do". Same with using damage reduction abilities on someone to save them.

But it's really about how fast you are yourself. If the poor processing and animation latency cause it not to work, you could in a lot of cases have pressed it earlier. In order to press it significantly earlier, I bind it to my mouse button, the same one I use for BLM's Aetherial Manipulation mouseover macro, because it makes it far, far quicker to use.