I was playing around in Training Mode for a few hours today, and here is what I found out:
Astral Heat can be backdash-buffered if you're fast enough... or if you play Mario Party.
Also, holding A+B+C along with a backwards direction allows you to barrier block while buffering your Ds. Just keep mashing D and let go of 1, 4, or 7 when you're ready (after at least 5 Ds).
With this in mind, you could theoretically barrier block the first few hits of a combo with 1/4/7A+B+C, instant block some if you want to gain more meter, and let the move loose when you see an opening, letting the HUGE magnetism suck them in for the win.
Also, the Astral functions as an unblockable, not a throw, so it can hit airborne opponents.