This might be helpful...
How writing a TV show would work in a perfect world: [Flashback to 2009] "Ok, we have 73 hours to tell the story. By hour ___, we need to introduce the Dornish characters and work out their individual arcs over ___ episodes, and the books say it should happen like this: [redacted; skip ahead 4.7 hours]. Let's get writing."
How it actually works: "Ok, so we're a go for Season 6. We need the Sand Snakes in this thing because they'll need to do ____, which is critical to the CENTRAL PLOT (which is what we have to focus on servicing first and foremost). So how can we get them from point A to point B with as little digression from the other, more established and interesting characters?"
How writing a TV show would work in a perfect world: [Flashback to 2009] "Ok, we have 73 hours to tell the story. By hour ___, we need to introduce the Dornish characters and work out their individual arcs over ___ episodes, and the books say it should happen like this: [redacted; skip ahead 4.7 hours]. Let's get writing."
How it actually works: "Ok, so we're a go for Season 6. We need the Sand Snakes in this thing because they'll need to do ____, which is critical to the CENTRAL PLOT (which is what we have to focus on servicing first and foremost). So how can we get them from point A to point B with as little digression from the other, more established and interesting characters?"