RE: Dumping the carcass by the road.
David, I agree it ain't a very smart or responsible move on the hunters part. If the deer are required to be checked at a deer station in your area, then yes it would be illegal and considered poaching of sorts. If it is suggested, meaning they would like for you to check a deer in but not required it is not.
Here we don't have check station but the disposal of carcasses and hides in a public place is illegal..not poaching persay but against the law. You could inform the GW about the site and maybe ask for clarifaction at the same time.