About uselessness, yeah, its healing capability is very low compared to the other healers or even to the old astro.
As not everything rolling around hardcore raidings and premade groups, i many time met tanks in daily roulettes whos rushing forward and pulling too many monsters, cause they think astro is whm or sch. But its not. So we wipe. No matter what lvl we talking about.
In old times i simply avoided this with the "The Bole" card, what will gives 10% dmg reduction, and with combined that with the tank def CDs, it was enough to let me heal out that tremendous dmg he takes. (Yes, i always had one stored for this situations.)
Now, i simply cant do anything to save the bold tank. Spaming heal and hope its enough. But mostly not cause its heals not that much as the other healers. As that, sch have the skill to still gives 10% reduction with her dome looking spell (sorry i dont know the exact name) and still have a fairy with her who will heal, not so high heals but still a help. Meanwhile she capable of putting double shield on the target what is a huge utility for her. And even have a spell that instantly heals a high ammount if the target fall under 50% hp.

So, now get a better look, what have the astro. DMG buff. Hmm... it will dont save anybody. Have a hot. Not realy a big help. Or if the dungeon is high lvl enough, then can be shielded as Nocturnal sect. But far not that strong as the schs shields. You have the 10% redu aoe, but that is a stationary spell, so until you channel it, you cant cast anything else otherwise you broke your own casting. And what else you can do? Hm, nothing. Watch, spam, hope. And meanwhile, not even enjoyable too for me. Dont have the feeling as the old one when i pull the card and see the possibilitys in it. Lost the feeling "YAAAY".
So overall, i simply lost interest and yes, as the astro have the most smaller dmg spells and the most smaller healing spells, advancing in MSQ or just open world things are very hard or even impossible with it.