Well actually it was 60 militia and 20 flagelants that got butchered by the slingers. But still you'd expect 10 elephant to be able to rout 60 lousy militia that have same morale as they. I think only 1 elephant actuality died, that's why I always use undead with elephants and cavalry.
It was a warp in the space-time continuum. We got the wrong battle results..... In another game, I fought ~10 Mammoths with 140 Skinshifters, and I lost over 40 men. I think the battle results were switched at birth.