I suspect that when the history of this era is written after all of us who were alive during the period are gone, a more complicated picture will emerge. A few of its elements...
Felt himself was imperious and arrogant, believing that the imperatives of national security allowed his beloved FBI extra-legal latitude, latitude which they might have been granted before Vietnam and Watergate shook Americans'
almost-unquestioning deference to the federal government.
Nixon and his Admininstration regarded the government as their plaything and the Constitution so flexible that it should have made these self-described "strict constructionists" blush.
The criminality of Nixon and Crew was so pervasive that, having become aware of all the crimes being committed, Felt had no official to whom he could take the information. (Irrespective of what Pat Buchanan has said.) The Attorney General was in on the conspiracy. So was the FBI director. Access to a grand jury would have been controlled by the Administration at the time. He had little choice but to go anonymously to Woodward or some other investigative reporter.
Conclusion: Felt may have operated from all sorts of mixed motives, as he and his family may be doing now in trying to cash in on his being Deep Throat, but he provided an indispensable service to the country.
The "good news" of Watergate was articulated by Gerald Ford on the day Nixon left the White House and Ford was sworn in as president:
Our Constitution works; our great Republic is a government of laws and not of men. Here the people rule.Would that we could still make that assertion so confidently, but the actions of subsequent Administrations, both Republican and Democrat may make us wonder.
By whatever route that Mark Felt arrived at his decision to be Woodward's and Bernstein's deep background resource, he played a pivotal role in an event which cleansed our political system, at least for a time. For that, he may be regarded, if not as a hero, as someone who, in this instance anyway, did his duty.