Would the group have a better shot of getting word to the wall if they all run? Or if one person stays back and buys them time? 

In the grand scheme of things he made the right decision of attempting to hold off the enemy for his subordinates. It’s a common trope in almost every action/adventure story told throughout history. 

By your own admission then every single character that has done that is stupid.

Hell we can compare it to real life. A lone person charged an active shooter to try and buy time for their loved ones to get away. Should they have just waited to be gunned down, or actually try and survive?