Moridin certainly considered the possibility that Rand might eventually kill Graendal in Arad Doman. I doubt, though, that Moridin really wanted this, because Graendal seemed like a pretty good tool for him and likely better to control than e.g. Demandred or Mesaana. He also warned Graendal to harm Rand, which implies that he didn't want her to directly confront Rand.