If it was simply a matter of surgical shooting, there were 9 Marine Scout-Snipers on the Boxer who could've easily taken those shots but that would over look the fact that dedicated Hostage Rescue is not a Marine Corps Role or Mission.
I had no idea there were already snipers on the destroyers. If so, you're correct the USMC snipers could have completed this mission, considering the final action that was needed to end the situation. Monday morning quarterbacking on my part. The SEALs were brought in for HR, which is one of their jobs. Nobody knew at the time, I'm sure, that it would boil down to 30 yard single shots to end the standoff. I concur with your statement. Apples and oranges.