Thats just the thing, you're using all those points on a single unit that can be (with good chances too) killed off by a Astral 1 spell. Works great until that happens though.
Hes already ethereal and Shinuama have access to same astral magic(lucky pendants/antimagic amulets) dont they? He already has plenty of buffing to do so why not just drop the astral magic(and maybe 1 level of dominion, 10 seems a little much on a ghost king) and buy some more scales?