I think the bad rap that AST got was in the beginning, because back then it WAS bad. Spells were just plain weaker, things like Disable were a joke (seriously, I'm going to predict when an enemy is about to cast something and then hit Disable first like a mind reader!?). All base heals are the same as WHM now, plus you can play in Noc if you want to do shielding (which is how I prefer to play. I enter an instance with another AST and immediately pop into Noc before they can lol). LA is a bit weird in that from what I understand it only reduces new enemity generation, not existing the way the WHM one does, forget if it's Shroud or Divine Seal, haven't played my WHM in awhile. My suggestion if you're having MP issues is when you draw a Ewer card, Spread it and hold onto it just in case for that extra. It also helps to put Ether potions on your hotbar just in case. At first I did have MP issues with AST but they are non-existent now.
Biggest tip I have for you is don't take this forum too too seriously. It's great if you have a specific question you want answered (like what does Refresh mean), but in terms of play style and so on everyone is different and as mentioned, most are referring to Savage content where the smallest things matter.
Remember too you can boost LA with your cards! When you get a Spear that's the best time to pop that on yourself and then LA, or if you have Enhanced or Extended royal roaded and then pop Spear and then LA, it will speed up when you can do LA again big time. You can even pop Celestial Opposition once you have LA up to extend it by 5 seconds more which is something like 1000 more MP for free! I try to always pop a Spear before LA or Collective Unconscious just to get it up quicker. It's the one thing I miss playing SCH, I always want to use a Spear card before popping Aetherflow before remembering there's no way to speed it up lol.
Btw I have 2 bunnies, Mr Worldwide and Hoppity

Rabbits are the best!!!!