Iago's mannerism

The mannerism of Iago’s revengeful plan towards Othello seems to be summed up pretty well, by the final quote of Act Two, “Dull, not device by coldness and delay.” Thus, Othello seems to be taking a gradual and subtle approach to this issue, rather than a quickly hostile plot. He is not trying to evoke the traditional plot method, but instead to act as a sly mediator that causes desired events to occur. For instance, he indirectly causes Cassio to be dismissed as an officer by telling him to drink. He makes a suggestion, and let nature run its course without interfering. The only time he injects his word, is when he gives advice to Othello, who trusts him as an honest man. So, it appears the substance of his plan is not to truly “plot” but slowly, but surely influences situations.
I think he does this mainly because it draws the blame away from his character. This truly helps him safeguard his evil instincts from being discovered. He makes himself look like a decent and trusting person to both participants, Othello and Cassio alike. Thus, neither one will suspect him, or lash out at him. He simply and subtly acts as helpful bystander, instead of a secret identity that is the cause of hostile problems. Therefore, the other characters become increasingly more trusting of him as time goes on. In essence, if something goes wrong, their perceptions will never be tilted toward Iago, because his style is intellectually sound.