[Amanaduial the archer]

It would add urgency, yes - but it would also probably be a little unrealistic. Think of any ruler - they wouldn't be left completely alone without and backup help, especially in a time of war. Even if it wasn't a very big force around Galadriel and Celeborn, there would still have to be some sort of force. This means it is still imperative that the envoy plus their help get back with the utmost haste, but it also means that the Lord and Lady will not be cut down as soon as the easterlings and orcs enter the palace.