No, it's definitely illegal, at least by the letter of the law.

But as long as you're only going a few miles over the speed limit for a few moments, nobody's going to write you a ticket for it.

One of many situations where the law in theory and practical application differ, since officers are given discretion (read: ability to apply common sense) in their duties.

It's not a perfect system, but it's what we've got.

Not in my state. And probably few, if any others. But it is a safety thing. The longer you spend in the oncoming lane completing a pass, the higher the risk of a collision (cars pulling out of driveways into the lane, people misjudging distances, etc.).

There's also what I've observed (not sure if there's an official name for it), that if you pass someone slowly, they will "lock tractor beams" onto you and start to match your speed. So you want to have a noticeable speed difference between your vehicles to prevent this.

Some good anecdotes here: https://www.quora.com/Have-you-ever-been-pulled-over-for-goi...

Oh for sure, but that could require going more than 10 over the limit. I can't imagine needing to go 25 over the limit under pretty much any (non-apocalyptic) circumstance, but 10 doesn't seem like sufficient for this type of situation.

Mirrors or not, hanging out in the blind spot is a dangerous place to be. You don't want to be there for any length of time longer than absolutely necessary.