If someone posts a very biased question that is likely to be quickly closed but I can see a way to heavily change the question to be objective (while preserving some of the intent) should I do so?
Don't be shy, make the edit. Sometimes commenting is appropriate for minor changes. Sometimes it's clear what a new user is trying to ask, but the question needs significant edits to get there. In that case, make those edits. Be respectful of the user and kindly solicit their input as to whether anything was lost in translation.
This can turn a question from a fight to close, which turns users away and gets our community labeled as hostile to newcomers, into useful content with lots of up-votes on the question and its answers. Personally, I think many users are too quick to down-vote without comment or criticize in a way that is opaque to outsiders, and too slow to give constructive edits.
Obviously if the original poster is not receptive and insistent on reverting edits, the question will have to be closed. This can be mitigated by being polite and sympathetic to the difficulties for new users to understanding the stack exchange model, but is sometimes unavoidable.
Making the edit without the support of the original poster often fails. Why? Because the original poster can edit the post back.
Take for example, this specific question. The original poster obviously wants to rant. The question has been edited to remove the rant twice. And it has been put back twice.
If you really think that the question has value, post your own question without the bias.
For previous discussion, see How to salvage the quality core of a question?