Originally Posted by
Helden
I've no doubt it would have looked pleasing, but it doesn't have the "wow factor" of wielding 2 swords, I mean who else have we seen in GoT who wields 2 swords? Daario is the only one I can think of off the top of my head, (though I can't remember whether its more of a sword and dagger combo) and he's a badass as well. It's something that makes him distinct, instead of being "generic bad guy #362".
I said in my first post that Dawn hadn't really been mentioned, but neither has Arthur Dayne to think about it. If you said to a show watcher, "holy shit Arthur Dayne is in this episode", they would have no clue who you are talking about, so they need something to set him apart, to make him look cooler than you average bad guy knight in armour, and dual wielding does that, especially in a show like GoT which generally has sword fighting realism nailed down.
and unfortunately "sword fighting purists" aren't generally a demographic that these TV shows aim at, because they are a very niche group.