Agreed, carelessness can cause serious issues. I see it sometimes but overall I would say most doctors (I in a tertiary care academic facility so obviously there is a bias) take their job quite seriously and understand the gravity of decisions they make.

It's proabably a waste of resources and time to have a 2-check method as protocol (doctors are already overworked). Often times it is present informally (radiologists/pathologists will often have their colleagus review problematic cases for agreement and neurologists and surgeons will frequently review the films)

What everyone should do is realize you can always get a second opinion and have another expert review the material.