Well, I was disappointed to not see much more of him, as he is my favourite character behind Rand.

However, regarding his overall plans, the first three books revolved around him trying to 'dethrone' Rand, by converting him to Shadow or killing him if not. He didn't succeed, but certainly tried, but at the same time was somewhat insane.

Then he was brought back, and his sanity restored, and was quite disappointed to be brought back. From then on though it seemed his main job as such was to help get Rand to the final confrontation (even to the point of helping in defeat Sammael), with his only other chance to succeed in his overall goal him without going against the overall plan being when Dark Rand nearly destroyed the world.

Other than that, trying to defeat Rand or kill him wasn't going to get his end goal, that of the Dark One breaking free and granting Moridin oblivion. What was made especially clear during Rand's battle with the Dark One, is that for the Dark One to break free, he needed the champion of light to give in. Killing the champion wasn't going to achieve this.

Thus at the end Moridin's only real hope in obtaining oblivion was for Rand to be at the final confrontation, and for the Dark One to win. I think deep down he knew that he had little chance in winning it for the Dark One, but gave it his best shot with Alanna and then the sword, but didn't succeed, and is doomed to be reborn again to fight the champion of light.