I am like some writer. I am also like some producer. And as a like some producer I can tell you they probably do have that shot of Tarly with his Dickon-face on looking shocked and scared. It's probably sitting on some editors Avid station right now in a group called "REMOVED". But between your 3 seconds of him looking as constipated as his son and Soygen wanting every single character to look into the camera and hold up their travel itinerary for us to read, some shit has to go. Showing Tarly doing X does nothing for the plot other than say "oh yeah this guy was here too". And it would seem you DO care about his arc if you're going to such lengths to be upset about these 3 seconds of screen time you missed out on.
I get that as a viewer you want to see X and need to hear Y but at the end of the day you have Z amount of time for an episode. Hell, your nerd rage could be directed at the assistant editors of the show for all we know.
And yes, I was incorrect in that Tarly was there for the entire battle. You got me. Even us like some writers can be guilty of bad TV watching.