While I will make the admissions that my AST is only 76 so I haven't got to play with it in 80 content. I dont think AST is dead. I agree that its currently the worst performing healer at the moment but outside of a certain situation I'll elaborate on I think AST is mechanically satisfying to play. Output wise, no it is weaker and I wont argue that.

The cards are the most controversial aspect so I'll start with that. I think they're mostly fine, SE seemed to choose consistency for the sake of balance over versatility and nuance. I'm ok with it myself but I understand and even miss the versatility of the old system. My issue with the system is Divination and Sleeve Draw. When you're simply cycling the cards between your Malefic and Benefic casts and slowly building up the seals for Divination between the cooldown windows it feels smooth. However, between Divination itself feeling too weak for the payoff and the fact you'll inevitably use Sleeve Draw along side it, whether to hastily set it up in an opener or to generate a bunch of Lords or Ladies to stack with it, It turns into clunky busy work. I believe if they can smooth out this particular part of the cycle, while increasing the payoff from Divination, then the system will be more satisfying to use.

There have been a few suggestions on how to address it, my personal favorites are Sleeve Draw automatically drawing the next card after you play it and Minor Arcana doing both the conversion and playing the card at the same time. I believe that would allow for the rushed feeling without the massive ogcd clutter. However I'm no game dev so I cant confidently say what would work best.

As far as the actual healing output goes, I agree it feels too weak, but ED feels great as always, same as Earthly Star when used properly. I'm also very fond of Intersection myself but I can see it needing a small buff. Horoscope I'm actually quite fond of, I do agree it can feel clunky and inefficient to setup but I have found it nice to have when I unlocked it. The elephant in the room to me is Collective and Opposition myself. These skills are what feel to weak to use in my opinion. Opposition either needs a significant potency buff or a cooldown reduction. But Collective definitely needs a buff to the regen, especially since Sacred Soil is superior to it in every single way.