The cattle call is one part of the problem. The second part is the overhead bin space on the domestic routes. Last week, flying TED MIA-DEN, they herded all of us in Group 1 aboard. That pretty much consumed 3/4 of the overhead bin space.
Then come the poor GM PAX and they find no space, but not until they get back to row 96, then the wheelaboard has to go all the way back to the front.
They really need to start redirecting luggage at the gate halfway through the boarding process. That alone cost us 10 minutes in late departure. I am sure some industrial engineer in Chicago has modeled this already and issued the approrpiate policy, etc. But it seemed really obvious to us as we watched these poor PAX schlepping their loads to the back, knowing there was no space available.