Yeah being on the weak side for a Lv 9 spell is what I'm afraid of. I just went ahead and made it 1/level for plane shifting or not since Plane Shift (5th level spell) already transports a flat 8 (which is more than 20/3), and Greater Planeshift (7th level spell) does it without inaccuracy. So this has the advantage of saving you the scry part of Scry and Die (though that means you don't actually know how many enemies are about at the moment), allowing you to bring more allies, and combining Gr. Planeshift and Gr. Teleport into one spell. All for +2 levels of spell slot and only being available as a domain spell so it's one way.