Dunno, I used to have Carrion Centaurs on duty of gathering manikins/mandragoras from all provinces to avoid losing many of those that way. Yeah raiding the provinces without commanders might work for reducing the numbers of those - still the OP says he hasn't problems with mandragoras/manikins in battle as much as with the carrion beasts, and those come in forest provinces which a smart Pangaea player would guard heavily. But reducing the high numbers of the base units might indeed be helpful
