I don't understand why Reactive Barrier is considered so weak.
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.
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.
I had derived it had another disadvantage. Spellstealing. Of course that's "too pro" for most people but I suppose some could predict who is the opponent and if it can steal it. Though to be honest I'm not sure if it's spellsteal-able. I haven't been offered a way to spell steal it from my addons so it might be not a reason. [if it triggers its CD, also dispelling is a problem]
Anyway, I think the talents mentioned here are both weak enough to just not be taken anyway.
and I agree if it was at least automatic without CD it would be better.
I believe its not used because it reduces the DR of your freeze in place abilities. SO your cone of cold and and frost nova last longer.
No you're thinking about Shattered Barrier, which was used before we gained CoC nova. Now it's a waste of talent points due to the sheer amount of novas we have a Shattered Barrier will DR our novas so that melee will be directly immune to novas for a short duration. That is something you really don't want when a Feral/Warrior is up your ass.
About reactive barrier the above posts are correct. The fact that it triggers and obeys your Barrier cooldown makes it just purely one of the shittiest talents a Mage has. It will almost NEVER be up when it should "proc".