[Maraxus]

That they can heal as a side effect of the ritual looks okay to me. Reavenants and Mount Kings can heal, too (iirc) and are quite skeletonish.

Moral 18 sounds enough. That should mean, that they will almost never flee because of losses and wounds but they might flee, if the opponent uses powerful fear auras and/or lots of fear spells.
And then the standard works perfectly with that to counter even that.