Revenge Tragedies, and Iago

Since I would consider both Iago and Hamlet to be based on revenge, I thought I'd look into whether they fit the bill for being called 'revenge tragedies.' So I looked into what exactly a revenge tragedy is.
Wikipedia lists these characteristics for a revenge tragedy:

• A secret murder, usually of a benign ruler by a bad person
• A ghostly visitation of the murder victim to a younger kinsman, generally a son
• A period of disguise, intrigue, or plotting, in which the murderer and the avenger scheme against each other, with a slowly rising body count
• A descent into either real or feigned madness by the avenger or one of the auxiliary characters
• An eruption of general violence at the end, which (in the Renaissance) is often accomplished by means of a feigned masque or festivity
• A catastrophe that utterly decimates the dramatis personae, including the avenger

Obviously Hamlet fits all these characteristics perfectly, but what about Othello? It might not exactly fit the bill, but I'd say it's halfway there. There is no secret murder, but a secret marriage, before the action of the play begins. No ghostly visitation: just Iago, practically without motivation (this may partly be why he seems so villainous, is because his real motives are so hard to determine). But after that it fits pretty well. Iago sets his plans in motion, which injure Montano, kill Roderigo, and injure Cassio. Othello, the auxiliary character is driven to madness by jealousy, "that green-eyed monster,"and in the end Desdemona, Othello, and Emilia. Sad day.

So what are Iago's motivations?

The first reason Iago cites is that Othello has promoted Cassio over himself to lieutenant. That is reason enough to be pissed off, but what about the body count? It's simply insufficient to motivate the mind games Iago plays with the Moor and everyone around him, even his own wife.
In the text, he implies that Othello may have slept with his wife, and that he would get even with him "wife for wife," even if it was just "for mere suspicion of it." It's almost like Iago is searching for any excuse to take down the Moor, assuring himself that Othello is "of a free and open nature," gullible to his machinations.

And the last thing he says in his first monologue just... irks. His comment that Othello will be "tenderly led by the nose / as asses are" reminds me of that scripture, 2 Nephi 26:22, where it talks about the devil leading saints away with a "flaxen cord." I find it also hypocritical, that Iago talks about how easy a target Cassio will be, and that "he hath a person and a smooth dispose / to be suspected," when the very thing causing his revenge is the rumor of revenge. Iago is setting his hate upon Othello, when he very well may be just the same as Cassio, with a 'person and a smooth dispose to be suspected.' David Snodin must have found Iago's character so enigmatic, that he made him the focus of a sequel to Othello, based around a "Fugitive" sort of plot: http://www.washingtonpost.com/entertainment/books/iago-by-david-snodin/2011/12/19/gIQA8r6BLP_story.html
That would be a fun read. :)