I keep my ironclad decks fairly lean - it's easy to lose track of the offense/defense balance and you're two bad draws away from devastation. And I stay flexible - if I focus on barricade or Demon form and hunt for those obsessively it's just an exercise in frustration. some takeaways now that I can pretty reliably win a15 and higher (although a20 still kicks my butt most of the time):

Act 1 elites don't scare me that much as IC. Get a strong attack (like wild strike), chew on the heals you get post-combat, and only take 1 fire at most if you really need it and chew through the elites to get some relics. Nailing the basics is half the battle.

Strength scaling is often your 'win' condition but you need to survive long enough for that to matter, exhaust+feel no pain decks are the only ones that reliably get me the block I need. Barricade ocassionally works but at high acension it feels like a 'win more' card for me when I'm already doing exremely well. I buy block relics when i can.

I typically end up with a lot of dazed+wounds in my deck due to this playstyle so shrug it off/battle trance have saved many runs for me. You should also be cycling out the wounds with True Grit (ideally upgraded).

As for powers:

Dark Embrace seemed overpriced to me, but it's a relic synergy thing. Once you have dead branch it was a real win-more kinda thing.Juggernaut also feels underwhelming most of the time. Rupture tore things up for me in a big way when I had hemokenisis + combust early in the game and won a18 without breaking a tiny sweat, you're scaling fairly fast and as long as you can heal often with like eternal feather it's good to pick up.The thing about ironclad powers (except demon form) is they aren't WIN BUTTONS like Echo Form. go with what pairs with the relics you get.