My assumption was that they left out the chain because they knew they couldn't stage all the ship-to-ship fighting that occurred in the book. They also, pointedly, left out the royal fleet, presumably for the same reason. From the looks of things, the prop department only actually built part of one ship.
Count me among those disappointed with the lack of epic scope in the battle. This show has done wonders using a combination of beautifully photographed natural vistas, matte backgrounds, and adroit misdirection to disguise its budgetary limitations.
It's very rare in GoT that you actually notice sequences where, in a movie, there would be a fully populated long shot with people moving around and full animation preceding a closer shot of a group of five or six people talking in a courtyard but here they leave out the long shot. They're very good at inferring or suggesting the conventions of epic filmmaking without actually executing them.
But here they walked right into their limitations. Somebody earlier mentioned that it looked like 20 guys fighting in front of 10 feet of wall. It really did; it almost rubbed our faces in its small scale: the constrained camera angles, the lack of an panoramic shots, the extreme briefness of the one shot of the Lannister army charging to the rescue.
In the book we see the battle outside the wall from Tyrion's POV, which is perforce the opposite of cinematic. This is how the series has managed to avoid having to stage big battles -- seeing them from the POV of someone who isn't there or whose involvement is limited. I expected the same for this one, and in fact I think that's what they were trying to do (show us Tyrion's battle, not the whole battle). It's just that there was so much hype about this epic batte sequence, going back even before the season began, that even the producers were caught up in it and did a poor job of managing the audience's expectations.
I'll say one other thing: no episode encapsulates for me the extent to which the writers are now condensing the story. Even GRRM, for whom having to leave out so much detail must be torture.