I think Arthas is the only character that didn't pass the process of dying, hence generating all this discussion. But again, all the Lich Kings never gone through a proper death. Ner'zhul was ripped from his body, Arthas passed the proper process of creating a Lich, by using Frostmourn as phylactery, and then stopping his bodily functions slowly, and Bolvar was kept alive, even with his body whithering, by Alexstrasza fire.
So, since the DKs of players are not candidates for the next Lich King, yes every one of them are reanimated corpses, but unlike forsaken and scourge, they appear to more like Arthas, and I can even say Gorefiend, and way more close to living being. For instance they don't have any reference about the lack of sensations Forsaken have.
Most of their senses appear to work as any living being work.