I love that, for ages, SCH was the uncontested ruler of PvP healing and barely anything was said about ridiculous it was to kill a scholar.
Now Astro ascends (hurr get it) to a strong spot and everyone stamps their feet and deems it impossible to kill them.

Here's an idea: CC.
Stun them. Sleep them. Silence them. There are a billion tools for crushing an Astro, especially in large groups.

Honestly, a sleep + raw destruction combo is usually more than enough to kill them anyway. And if your other complaint is that it's hard to kill them in smaller groups: It's SUPPOSED to be. They're HEALERS. They're supposed to tank and bait you.