Clinton will probably skate. And yet she'll be the first person demanding that we try Snowden and keep Chelsea Manning locked up.
There isn't that much statutory groundwork to support charges and what there is says an agency head "is assumed to be acting under executive authority", i.e. as the arm of the President.
The Congressional Research Service wrote a rather helpful summary[1] of the myriad aspects of classification and law.
[1] https://www.fas.org/sgp/crs/secrecy/RS21900.pdf
But yeah, if you or I were to do what she did, big difference - just not all because of politics.
The fact that 10-15% or so of those emails needed a retroactive security classification demonstrates that she held either had a cavalier attitude toward guarding that information, or was simply incompetent in knowing what should and should not have been classified.
Whether that rises to the level of a criminal act, I suspect, depends on whether any of the 30k+ emails she deleted, claiming they were personal, also contained classified material, because then the crime is lying to the FBI more so than the reckless handing of classified information.
For example if one of Clinton's friends forwarded her a NYTimes story about CIA activity in Syria, and she forwarded that to a deputy, well, now she has both received and sent classified information from her email.
And even though it might have been on the front page of a newspaper, a retrospective review would designate it as classified information.
Would a staff-level person get fired in that situation? I don't know. So much stuff is classified these days, and yet the press is pretty good about ferreting out stories. Any regular reader of the major news operations is probably going to see classified info on a regular basis.
How easy is it to keep track of which public, well-known news stories should be excluded from nonsecure email? I would guess, not that easy.
I think the rationale is because sometimes the file gets updated internally such that the leaked info is no longer accurate and the person with access might screw up.