There are reasons for these policies. Part of being a "good and competent" nurse is not being afraid to ask a co-worker to double check you, especially with medication doses. If a hospital has a policy that a nurse doesn't feel is worth following, and something bad happens, they'd better hold onto their a$$ because it's going to get rough.
My facility used to require a double check of Heparin doses, and still does require double-checking of insulin doses. We often ask another nurse to double check other drug calculations. It is not a sign of being incompetent, it is a sign of caring, making sure you get the correct dose for your patients. I have double checked other nurses when they've had a question or felt uncomfortable with a dose calculation, and they have double checked me. It's just good nursing care.