All rocker shafts should have some sort of saddle type brace under the bolt head. It's not so much for reinforcement it's also for spreading out the clamping load.
With the stock set up you're using a small flat bolt face to hold down a hollow piece of round tube. What you end up with is only two contact patches, in the shape of a line, from the bolt pushing down on the very top tangent of the rocker shaft. With very little torque the shaft collapses under the clamping load of the 3 bolts. What that does is stresses the parts of the shaft where the hole is drilled for the bolt (the weakest part of the shaft). When they break, it's always at that area.
A radius saddle type clamp/washer will allow the clamp load to push down on the shaft itself instead of forcing it to deform before the clamp load comes up. Keep in mind pressure is measured in pounds per square inch. The saddles I built offer .82 square inches of contact area per saddle. A long bolt offers about 1/200th sq" and grows as the shat flattens out and gets stressed.
There's been plenty of broken rocker shafts with stock cams over the years (I even broke one). Any larger cam, fast ramp speed cam, or stiffer spring setup needs some saddles.
