yep that's what i wonder always too stormbinder
it's one of the few features dominions is missing .
in aow 2 shadow magic this worked very well for me
once i was strong enough i disbanded my quite useless cheaper units
it would perhaps enchance national units a bit even because you can buy them in the beginning to expand and don't need to bother if you sacrifice them later .
and another similiar problem is the sucky militia you get as a "good" luck event