They were the best sound had to offer. If they were orochimaru's personal guards, i personally cant see them as weak. especially if they were able to errect a barrier Leaf Anbu couldn't penetrate. Add to that their respective bloodlines... they were great shinobi. They lost only because killing...
But wouldn't the byakugan be able to see the chakra of the person using this strategy and attack by focusing on the chakra alone? I know becides Hizashi (i think that's right) there are no edo tensei byakugan users, but im just saying in general.