Considering AST is just WHM and SCH slapdashed together with a gimmick? Designing healers in this game is actually egregiously difficult in due to how it's designed. For example, the slow GCD and the heavily scripted nature of fights involving burst damage would never let a HoT based healer work. Or a healer that channels spells over time wouldn't work because you should be spending GCDs on DPS and maximizing OGCD usage for healing. The only thing that -might- be workable is a melee healer, and even then the actual difference would be negligible in due to the overarching game design. Again.
Sucks for people who wanted a healer, I totally get why you're disappointed, but it's just extremely hard to actually work with making a new one. For what it's worth, I'm horribly concerned with how Gunbreaker is going to play seeing as SE had the 'brilliant' idea of giving every tank fell cleave in 4.X.