Shieldwall was tier 1 last season as shown by this and meta reports shows that it's still tier 1 this season. That's exactly what people have been saying. Keep in mind this is after pretty much everyone has been forced to tech against it.
Actually, shieldwall is a strong deck. But a win rate of 53 % at Pro does not make it completely overpowered. My point is that at a balanced game at best all win rates of the different leaders would be between 45 and 55 per cent. So improving all those <40 pro Rank leaders should be Prio 1.
Talking about the dominance of shieldwall and what to do against it:
Mostly you face two different types of NR decks.
1) Decks with no shield units but with many units you want to protect with your shield orders (e.g. Vysagotta, Kerack Frigate, Baron, War Elefant, Viraxas, Anna Strenger compare
https://teamleviathangaming.com/meta/).
This strategy appears to be one of the strongest currently. To my mind the most obvious card which should face a nerv is Kerack Frigate. It´s a 6 provision card with 4 value + 2 engine each round.
If you compare Kerack Frigate with
Lieutenant Von Herst you see another card which basically offers the same value (4 provisions + 2 engine each round) for 8 provisions. One might argue that the firesworn token is more valuable or that crew is more easily achievable than hoard 4. But this does not explain that huge difference.
So I would suggest: Kerack Frigate (2 strength, 3 armour, Order: Spawn a Volunteer in this row. Crew: At the
beginning of your turn, refresh this ability.)
Furthermore, one might discuss whether Anseis should get Veil.
2) Deck with many shield units, fewer units you want to protect with your shield orders and King Roegner as a finisher. Sucess of this deck heavily depends on whether you win round 1, because you want to play Roegner as your last card in round 3. Additionally it depends on the ability of your opponent to remove your shields. I would argue that this deck is definitely not overpowered.