Were their objectives the same or better yet were their expectations of Hagen? Somehow I don't think that Vito wanted Michael to be as cold to Hagen as Michael ended up being.
As I opined in other posts, Michael had Vito's intelligence, but little of Vito's familial empathy and sympathy. Vito definitely did what he did (as horrible as some of those things were) for his family. Michael ostensibly did things for his family, but only for his own aggrandizement. He used his family.
Michael never forgave Tom for Sonny's death. Even before that, he was jealous of Tom's brother relationship with Sonny. Vito agreed to cut Tom out of the massacre because if Tom's participation was discovered, that would break the peace. Also, I think that Vito recognized that Tom did not have the skills of a wartime consigliere. That was true.
