I will somewhat agree that it is a PvP talent, but any experienced PvP opponent that has gone up against a SPriest knows we are only like that for 6 seconds and times attacks for when we are coming out of our shadowy little cloud. They also know there is nothing we can do for 6 seconds except move around and can take time to bandage or heal. And once we use it they know we are on CD. I would not mind seeing a mechanic like all Shadow based DoT's on a target take an additional 25% damage while the SPriest is dispersed. I would even be willing to drop our damage reduction down to 75% for something like that.

As far as PvE I find myself using it everyday when I run a random heroic. The majority of tanks now are so over geared for most heroic dungeons they routinely try for speed runs. They pull entire rooms and hallways and leave it to us to burn them down. We have decent mana regen but Mind Sear is a mana hog. I find myself dropping down to 5k mana quite a bit, and being able to hit Dispersion when it is off CD for the quick boost is more than welcome. I can't remember the last time I had to pop a Runic because I was running low.

I have also found it useful when doing runs with inexperienced healers that are concentrating on the tank and are forgetting about us. And especially for the trash mobs in ICC. I have yet to run with a tank that can hold ALL the trash once my DPS ramps up over 20k during a fight. Fade helps but unless I am hitting it and running in the opposite direction they will be right back. Dispersion has saved me a few times.

Is it broken? I'm not sure. I have not played my SPriest beyond the 3.3 patch so I do not know the history. I am happy that we have the talent but I do feel it could be lower in the tree for what we are getting.