I've never seen an AV take more than a single step since mods were introduced and I started making full use of the speed mods/traits on AoMr. Not once. I'll admit, I don't play the higher levels of difficulty, and I don't run across AVs a whole lot, and I only saw it happen once. What I remember of that time was that the living and dead AV were both within LOS, though. It wasn't on the most recent version, either (a beta as I recall), but we probably would have heard of it if something like AVs leaving a corpse was changed. I may test this at some point, and if it happens again, you can bet I'll take a screenshot of it.