I have the same problem, D3's randomly crashing/freezing specially when there is a large mob spawning. Everything works fine if I just leave my GPU to stock, but when I OC my GPU that's where the problem starts.
This is what I did to solve the problem.
Check your AMD drivers first, if it is 12.4 uninstall it and use 12.3 drivers, I read from some random forums that D3 is not fully supporting 12.4 drivers at the moment.
As of now, I am playing D3 on my 7850 @ 1190/1475 with no issues at all.
I hope what I did can help you solve your problem as well.
Edit: Typo at the clocks