Modifications for Horde attrition

Hello all, I've been looking without success for some way to add a very small amount of attrition to the Aztec, Mongol, etc. event troops. Either as a mod or an edit to the relevant game files. Obviously they should still be scary, world-shattering enemies, but as it stands unless you, the player, are quite scary yourself there is little to stand in their way and I'd like to even the odds just a little for all the "middle powers" out there.