I think AST is only marginally more difficult. I was very daunted by it at first because of the difficulty hype. I also felt the razor thin margin of error thing at first, some mp issues, and some not fully understanding the class issues. Now with Luminiferous Aether giving a longer refresh, just spam that Benefic II whenever you need it, you aren't going to run out of mp. Don't be afraid to use your abilities during trash pulls, LA, Lightspeed, Synastry, most of it has a short enough CD that in another 2 minutes when you get to the boss you can use it again. Use your buffs on trash pulls, I try to royal road either an ewer or spire (for AOE) for as many trash pulls as possible. I was playing my AST like it had a razor thin margin of error, and so it did. However now I main AST and I think it has more utility, and more ability to save a hairy situation than the other 2.

Stick with it, and go get Swiftcast it will save your life ALL the time.