I also fail to see why some people think Dispersion does not fit as a 31 point talent. It's true that on its own, it may be a little weak compared to the 31 point talents of other classes. In fact if every class had only ONE talent in their trees and that talent is the 31 point talent, then dispersion would probably the weakest.
The issue does not lie within the 31 point talent itself, it rather focuses on our other talents as well as our other abilities. If all our other talents are marginally stronger than other classes, then it would only make sense that our 31 point talent would be made a bit weaker if everything needs to be balanced. Remember that other classes NEED the 31 point DPS talent in order to balance out their damage. For us, our damage is ALREADY balanced without it, so in terms of DPS, we don't even need a 31 point talent. Why debate about a DPS talent that we don't need? If hypothetically our 31 point talent is changed to a DPS increasing talent in the next build, then that will definitely result in a nerf in some other aspects of our damage.
The bottom line is that everything needs to be balanced. Not just DPS, but survivability and mana regen as well. Blizzard doesn't really care about what goes where as long as it's all balanced at the end of the day. If they see that we can use a bit of regen and survivability, they'll give it to us. And if the 31 point talent is the only place they can find to give it, so be it then. If they see we can use a bit of burst for cata, they'll give it to us too, via Mind Spike.