I mean, Anduin really IS that ballsy to hang out there, because it would be really easy to just grab him and go. (Though, he DOES bubblehearth at the first sign of trouble. THAT ALONE IS IT’S OWN QUESTION. TO WHERE DOES HE HEARTH!?!?)
Don’t try to think too hard about heartstones. Thrall uses Astral Recall at the beginning of the Deathwing fight, and ends up on a platform in the Maelstrom. I don’t think he set his hearth there (but I could be wrong.)