Game Of Thrones Season 7: 7 Things You Might've Missed In 'Eastwatch'
2, Swing The Sword, Break The Wheel
Daenerys burning Randyll and Dickon Tarly to a crisp has been seen in some quarters as a sign of her madness, but it could also be considered the mark of a good (or at least honest) leader. One of the first pieces of wisdom we hear on the show is that "the man who passes the sentence should swing the sword", and that is - sort of - what Dany is doing here.
It's a contrast to Season 5. Back then we saw her let Daario swing the sword on an execution she ordered, and even looked away while it happened. A week later, we saw Jon - ever his father's son - execute Janos Slynt himself. It's not 'nice' what Dany does to the Tarlys, but if Drogon is considered her sword, then it's more befitting of a ruler. Whether it's not swinging the sword or doing it without proper reason, we've seen this hurt characters before (see: Joffrey and Theon), so Daenerys is doing the right thing here, in a sense.
During the same scene, we also hear Dany say: "All I want to destroy is the wheel that has rolled over rich and poor to the benefit of no one but the Cersei Lannisters of the world." This comes in reference to her big 'break the wheel' speech from Hardhome (another episode where Jon heads beyond the Wall, no less).