It's quite simple. The prohibitions against cloning and genetic manipulation, and the cautious nature of Amarr scientific progress, means they are the obvious choice to be first to deploy such things.
The Dust novel will probably start off as follows:
Evil priests find an evil Sansha troop doodad, and reverse engineer it in their evil science chapels, and present their findings to the evil Amarr Navy evil admirals, who all shout "hurrah, this will enable our evil schemes to proceed evilly. The Evil God be praised, in an evil fashion!".
Thus, the evil troops are evilly sent out to further evil plans to spread evilness, evilly.