I'm glad your husband spoke to the head server, but after receiving the complaint from the server, it would have been better for the head server to speak with you and others on the table. When he/she visited your table, they could say "If there's anything I can do to make your dining more special, please come and see me". We are usually asked at the table if everything is fine...but in this situation, if he invites you to see him, it's a good way for him to signal that he knows there's an issue and he would be happy to speak to you about it. I don't believe he can do anything unless a guest says something. And sometimes people don't want to complain and just accept the miserable situation.
If the head server had done something after the server complained (before your husband spoke to him) your story would be different. This would have been a story about how great your head server was for being aware and engaging so that you have a wonderful dinner experience. Don't get me wrong, I don't believe that Head Servers could see all the issues that are happening, but the fact that the server had spoken with him/her, then that should signal their attention is required.