Most people compare it with Invocation and immediately proclaim it worse. But I think they are very impressed by the wording of Invocation but it's mainly wishful thinking.
i.e.
The common way of thinking
1. Reactive barrier works ONLY if it procs below 50% hp.
2. Invocation is AWESOME. I will do amazing damage after I interrupt any nab.
But the story has two pictures here, or more precisely, a wider picture:
1. Reactive barrier will ALWAYS work, without a GCD when it goes below 50%hp. It will increase the effective health of the player immensely which is the main reason pvpers stack resilience. It will increase damage indirectly, and CCing, since it will not trigger a GCD. All those 3 shields trigger 3 different GCDs. This is huge. It stops dpsing and ccing while one waits for them to go out of GCD cooldowns.
2. Invocation will work *IF* you have the time to do damage. If you are stopped, it will have no benefit. Also, there may be defenses up that do not make it very impressive. Also, 10% is not really THAT impressive. e.g. If something that could crit doesn't, it's already 50% down there.