I don't like that it replaces shear. I get the limited charges but I'd hate to be out of pain with both fractures on CD for several more seconds. When you need it, you need it. I don't think it should replace.
As of right now, if anything we have TOO MUCH pain on the alpha. We'll see how it ends up at max level but right now you literally have to use 0-2 Soul Spirit Bombs just to not pain cap if you talent both fracture and spirit bomb.
I think they increased the amount gained from taking damage. Some testers on the official forums said pain generation was not a problem at all and was capped a lot.