Why do I keep breaking rocker arms?

? You can remove the rocker assembly and put a straight edge across the valve stems and get a good idea how bad off they are.
In the same vein could put a dial indicator on the lifter and measure cam lift off the base circle. That will provide a decent idea of the cam even without checking timing at .05 and which wouldn't be that much harder but is more work to set up tape or a degree wheel.