Personally, I think the devs need to choose if AST is going to focus on HoTs or mitigation, design the job around that, removing the sects, and add a new healer in the future to take up the dropped sects place.
As it stands, the balance between N.AST and SCH changes far more radically then between D.AST and WHM, with one receiving a buff and making the other inferior.
I think the sects also create a balancing issue within AST themselves because both are pretty much treated as two separate jobs in hardcore content, valuing different secondary stats and using their respective effects at different times (before or after a big hit).