Judging by the unit description, the Shuten-doji should be a capable commander:
Shuten-doji
I don't understand the exhaustion field myself, but would a retinue of blood slaves contribute to auto-rout, or would they just fall down and allow him to feed off of them? I think that might be a thematic and grisly way to handle this guy.
If he kills friendly units with his aura, or music, or whatever the field is, his life drain ought to absorb friendly life force, no?
The other problem might be abuse if empowered in blood, but how big a retinue is required for such abuse?