Maybe I've misread your intent with this bit, but I don't see how Paddy Considine/Viserys being an unconvincing king is a criticism? He's supposed to be weak, it's what his cuts from the Iron Throne are symbolising. The Throne was built by Aegon the Conqueror from the swords surrended by his enemies and is intended to be uncomfortable as "a king should never sit easy" (This version is far closer to the monstrosity described in the books than the GoT version) and it is said in the novels that being cut by the Throne is akin to the Throne rejecting the King, one early King, Maegor the Cruel, was even killed on/by the Throne with slashes down his arms and a blade protruding out under his chin from the back of his neck.
This is intentional. Caraxes, Daemon's dragon, is described as being red, huge and lean, and is also nicknamed "the Blood Wyrm". It's supposed to be this funky looking thing compared to the other dragons, which to me have looked fine in the show so far.