Lighter wheels with fewer spokes require more tension and are going to have more problems than heavier wheels with more spokes. For me personally, I'm willing to accept less reliability for race day equipment under the assumption that it's lighter/faster and I won't be putting very many miles on it. But for training or my commuter bikes, I want the stuff to last and not worry about it leaving me stranded. So I put up with a little more weight. My touring bikes are built to be bombproof but not excessively heavy.
Two cracked rims in three years does seem excessive but if you don't want to keep dealing with this get some more reliable wheels. I don't think it's a manufacturing defect but rather a design defect or a result of using the wheels in an inappropriate application (i.e. lots of training miles on rough roads.)
IMO I don't like Mavic wheelsets due to all the proprietary stuff. Special spokes, special rims, special nipples, etc. I'm much happier with my Shimano hubs, standard j-bend or straight pull spokes, normal nipples, and normal rims. That way if something DOES go wrong I can actually fix it without hunting for parts or paying through the nose.