Astrologian
Rotation/Damage
AST has always been a bit of a weaving problem, and 1.5s malefic always seemed pretty boring to me. There's nothing to manage, aside from adapting to the awkwardness if you're used to full cast times.
Malefic goes back to 2.5, and AST gets an instant spell - let's call it Stella.
Every Combust tick has a 40% chance to upgrade Stella into Cluster. Cluster can stack up to 6 times (maybe have it show on you with a cool orbit, sorta like Neutral Sect does?)
Cluster does equal or more damage than Malefic, so AST now has a Ruin2/4 deal going on.
Managing weaving (because AST has a lot of that) and efficient proc usage in buff windows is a bit more interesting than a 1.5s cast time, methinks.

Healing
AST currently has the most interesting healing kit of the 3, since the a couple of the skills aren't just "+HP, +Regen, or +Shield". So I don't really know what I want. Other than removing Sects so that AST can shine on its own light rather than being
NotWHM or NotSCH.
I'd like to see more skills utilise the delay=stronger or lowhp=stronger. Those are neat.

Utility
Cards. Damage. Maybe utility too. I'll not delve too deeply into this, and you shouldn't either. Most of the suggestions I've seen on this forum recently are stupid and bad and if I see you discussing them in this thread too I will quote this part of the post and shame you for your lack of reading comprehension

Feel free to add what you like - I won't stop you from making suggestions, but I will point out why you are wrong.