The job is completely reliable in all end-game content, any notion that it isn't is a player issue. AST regen ticks/potency isn't much of an issue, aside from the amount of GCDs you could have "free" on WHM compared to AST over the course of a long fight if you got full value from each tick. The latest potency enhancements to AST healing potency was in my opinion to make up for not having the MND buff when replacing a WHM. On the other hand you also have to manage healing differently, Aspected Benefic has the front-loaded heal over WHM Regen, which is why it costs more MP.

Range "issue" is a bit overblown. Stems from White Mage mains being used to 20y Medica II. Scholar skills including Whispering Dawn is 15y. Of course someone will say they are not the main healer, and yet they were given an enhanced AoE toolkit this go around, albeit with resource usage. In the end it takes is raid and postional coordination.