Not trying to be provocative or anything. I would like to share a recent run with the Ironclad on A1.
I didn't visit any merchant in Act 1. The first card reward I chose was rampage. So I decided to go for a small deck. When I finally visited a merchant in Act 2, I already had 500 gold. So I bought the colorless power card Fasten. At this point I can basically take down regular enemies hitless. Then I went for as many elites as possible. After getting the Icecream from an elite, I was unstoppable.
The final fight with the Doormaker was a little tough at the beginning, because I didn't pay attention to how its intent changes. Soon I figured out the right strategy. When it exhausts any card you play, just play regular defense cards. You have next two turns to deal a ton of damage. With such a small deck and the help of Soul cards, my rampage was able to deal over 100 damage in the last turn.
The most important item in this run is definitely the icecream. Without it, I wouldn't be able to play many cards when the Doormaker eats my energy for every card played. Maybe I won't get this lucky in future runs, but the new mechanism of the Doormaker is really fun. I like it a lot.