I've never really been a healer main. I keep my SCH geared because I get it leveled for free by leveling my main and tend to have more uncapped tomes than I know what to do with, and I play it whenever my FC needs a high level healer for something more than it needs a high level DPS, but it's far from my favorite class to play. I don't remember much about pre-5.0 SCH, but I do miss having more than one DoT.
That being said, the 5.0 changes ruined AST for me. I was enjoying leveling it back in the 4.x days, got it to 50 along with WHM, and vastly preferred AST to WHM because of the card system and the different things I could do with it. I liked that every card was unique and while dropping a Super Balance (at least that's what I called it in voice chat when I had a Balance drawn with the "increased power" effect ready) right at the start of boss pulls was fun and all, the thing that really sold the class for me was that, at least in low-level dungeons where you didn't have all your fancy oGCD buttons and a lot of players weren't playing anywhere close to optimally, every card had a purpose.
Of course Balance was the best, because it was the DPS card. But I still got plenty of use out of the others, whether it was Ewer helping me manage my own MP (and giving me reason to laugh at a BLM who insisted I give him all my Ewers "so he doesn't have to do ice phase"), or Bole saving the sprout tank who overpulled and can't find his cooldowns.
Nowadays, all the cards are mini-Balances, which I find INCREDIBLY boring, and they had to add some convoluted-looking seal system in order to justify still having six base cards instead of just "the melee card" and "the ranged card". I'm gonna have to level this eventually if I want my Soul of Magic title, but I'm REALLY not looking forward to that...