Re: When all else fails, find a scapegoat.
Administrators don't go back and re-do all the testing. All they can do is ensure that the checks and testing was done, and the paperwork supports that it was done correctly. That IS the essence of administration in a free-market economy.
Now if the sub-contractor (Orbital Sciences in this case) does that testing incorrectly, or incompletely, or incompetently, then they are at fault, and they have insurance to cover that business eventuality. Their reputation suffers, and their insurance rates will likely increase per launch. NASA has no responsibility in this instance...nor should they. Being administrators means they orchestrated the launch, ensured Wallops was ready, and ensured the area around it was clear for launch (oops). That is what an administrator does, not reverse engineer the engine, re-perform the testing, etc. By all accounts, Wallops was ready, NASA tried to ensure the area was clear, and ensured what would have been a safe and successful launch had the sub-contractor been successful.
NASA is entirely blameless, IMHO. There is a culprit, and that is whomever inspected and certified those engines most likely.