Indeed it is. They don't have the manpower either. They could be relieved by some boarding and pre-inspection of ships capable of carrying illegal passengers and weapons. We also have a corruption problem in that area and I think that a back-check by a competing agency would improve the effectiveness of the Customs Authority.
My interest is to see more patrolling for illegals and contraband weapons. Do you have a problem with using the USCG for that purpose?
If they had the additional manpower...no. But since they don't, and they have similar training like the Navy, it makes since they help secure our naval forces. And no, the Navy doesn't have the resources to maintain perimeters without shooting people out of the water. The USCG has small craft just about everywhere which can help maintain those perimeters.